#18: implement SMTP Submission (587/465), SASL PLAIN/LOGIN auth and preflight diagnostics

services/protocols/internal/application/port/auth_repository.go

@@ -6,10 +6,15 @@ import (
 	"github.com/google/uuid"
 )
 
-// MailboxAuth is the subset of mailbox data needed to verify a login.
+// MailboxAuth is the subset of mailbox data needed to verify a login and,
+// once authenticated, to apply the sender policy of PLAN.md section 5.2.
 type MailboxAuth struct {
 	ID           uuid.UUID
 	PasswordHash string
+	EmailAddress string
+	DomainName   string
+	// MaxRecipientsPerHour caps a compromised account's blast radius.
+	MaxRecipientsPerHour int
 }
 
 // AuthRepository resolves a login address to its stored credential.

services/protocols/internal/application/port/imap_folder_repository.go

@@ -4,11 +4,11 @@ import "context"
 
 // ImapFolderRecord is the IMAP-relevant subset of a folder row.
 type ImapFolderRecord struct {
-	ID          string
-	Name        string
-	UIDNext     uint32
-	UIDValidity uint32
-	NumMessages uint32
+	ID            string
+	Name          string
+	UIDNext       uint32
+	UIDValidity   uint32
+	NumMessages   uint32
 	HighestModSeq uint64
 }
 

services/protocols/internal/application/port/outbound_repository.go

@@ -2,6 +2,9 @@ package port
 
 import (
 	"context"
+	"time"
+
+	"github.com/google/uuid"
 
 	"lambdamail/protocols/internal/domain/entity"
 )
@@ -10,4 +13,9 @@ type OutboundRepository interface {
 	Enqueue(ctx context.Context, job *entity.OutboundJob) error
 	FetchNextReady(ctx context.Context, workerID string, limit int) ([]*entity.OutboundJob, error)
 	UpdateJob(ctx context.Context, job *entity.OutboundJob) error
+
+	// CountRecipientsSince reports how many recipients a mailbox has queued
+	// since a point in time. It backs the per-mailbox send limit that keeps a
+	// compromised account from becoming a spam source (PLAN.md section 5.2).
+	CountRecipientsSince(ctx context.Context, mailboxID uuid.UUID, since time.Time) (int, error)
 }

services/protocols/internal/application/usecase/inbound_auth_test.go

@@ -0,0 +1,140 @@
+package usecase
+
+import (
+	"bytes"
+	"context"
+	"net"
+	"strings"
+	"testing"
+
+	"github.com/google/uuid"
+
+	"lambdamail/protocols/internal/application/port"
+)
+
+type stubAuthenticator struct {
+	result port.InboundAuthResult
+	seen   port.InboundAuthInput
+}
+
+func (s *stubAuthenticator) Authenticate(_ context.Context, input port.InboundAuthInput) port.InboundAuthResult {
+	s.seen = input
+	return s.result
+}
+
+func inboundInput(recipients int) ProcessInboundEmailInput {
+	in := ProcessInboundEmailInput{
+		Sender: "sender@sender.test",
+		Body:   bytes.NewBufferString("From: sender@sender.test\r\n\r\nbody"),
+	}
+	for i := 0; i < recipients; i++ {
+		in.Recipients = append(in.Recipients, port.MailboxRecord{ID: uuid.New()})
+		in.RecipientAddresses = append(in.RecipientAddresses, "rcpt@example.test")
+	}
+	return in
+}
+
+// The verdicts must reach the database, otherwise the webmail and the DMARC
+// dashboard have nothing to show (PLAN.md section 6.1).
+func TestUseCase_Handle_PersistsAuthenticationVerdicts(t *testing.T) {
+	messages := &recordingMessageRepository{}
+	uc := NewProcessInboundEmailUseCase(nil, &capturingBlobStorage{}, messages)
+	uc.SetAuthenticator(&stubAuthenticator{result: port.InboundAuthResult{
+		SPF: port.AuthResultPass, DKIM: port.AuthResultPass, DMARC: port.AuthResultPass,
+	}})
+
+	if err := uc.Handle(context.Background(), inboundInput(1)); err != nil {
+		t.Fatalf("Handle: %v", err)
+	}
+
+	got := messages.persisted[0]
+	if got.SPFResult != "pass" || got.DKIMResult != "pass" || got.DMARCResult != "pass" {
+		t.Errorf("stored verdicts = %q/%q/%q, want pass/pass/pass", got.SPFResult, got.DKIMResult, got.DMARCResult)
+	}
+}
+
+// RFC 8601: our own checks must be recorded in the delivered message so the
+// spam filter and the user can see them.
+func TestUseCase_Handle_PrependsAuthenticationResultsHeader(t *testing.T) {
+	blobs := &capturingBlobStorage{}
+	uc := NewProcessInboundEmailUseCase(nil, blobs, &recordingMessageRepository{})
+	uc.SetAuthenticator(&stubAuthenticator{result: port.InboundAuthResult{
+		SPF: port.AuthResultPass, DKIM: port.AuthResultNone, DMARC: port.AuthResultPass,
+		AuthenticationResults: "mail.lambdamail.test; spf=pass; dmarc=pass",
+	}})
+
+	if err := uc.Handle(context.Background(), inboundInput(1)); err != nil {
+		t.Fatalf("Handle: %v", err)
+	}
+
+	if !strings.HasPrefix(string(blobs.stored), "Authentication-Results: mail.lambdamail.test") {
+		t.Errorf("stored message does not lead with Authentication-Results:\n%s", blobs.stored)
+	}
+}
+
+// A sender that published p=reject asked for exactly this. Accepting the
+// message instead would defeat the policy the sender is paying for.
+func TestUseCase_Handle_RejectsOnDmarcFailWithRejectPolicy(t *testing.T) {
+	messages := &recordingMessageRepository{}
+	uc := NewProcessInboundEmailUseCase(nil, &capturingBlobStorage{}, messages)
+	uc.SetAuthenticator(&stubAuthenticator{result: port.InboundAuthResult{
+		SPF: port.AuthResultFail, DKIM: port.AuthResultNone,
+		DMARC: port.AuthResultFail, DmarcPolicy: "reject",
+	}})
+
+	err := uc.Handle(context.Background(), inboundInput(1))
+	if err == nil {
+		t.Fatal("expected the message to be refused")
+	}
+	if !strings.HasPrefix(err.Error(), "550 ") {
+		t.Errorf("error = %q, want a permanent 550 rejection", err)
+	}
+	if len(messages.persisted) != 0 {
+		t.Error("a DMARC-rejected message was stored anyway")
+	}
+}
+
+// Quarantine is a filing decision, not a refusal: the message is accepted and
+// the spam filter decides where it lands.
+func TestUseCase_Handle_AcceptsOnDmarcFailWithQuarantinePolicy(t *testing.T) {
+	messages := &recordingMessageRepository{}
+	uc := NewProcessInboundEmailUseCase(nil, &capturingBlobStorage{}, messages)
+	uc.SetAuthenticator(&stubAuthenticator{result: port.InboundAuthResult{
+		SPF: port.AuthResultFail, DMARC: port.AuthResultFail, DmarcPolicy: "quarantine",
+	}})
+
+	if err := uc.Handle(context.Background(), inboundInput(1)); err != nil {
+		t.Fatalf("Handle: %v", err)
+	}
+	if len(messages.persisted) != 1 {
+		t.Errorf("persisted %d messages, want 1", len(messages.persisted))
+	}
+}
+
+// SPF is defined over the peer address and the HELO name, so both have to
+// reach the authenticator.
+func TestUseCase_Handle_PassesPeerIdentityToAuthenticator(t *testing.T) {
+	auth := &stubAuthenticator{result: port.InboundAuthResult{SPF: port.AuthResultNone}}
+	uc := NewProcessInboundEmailUseCase(nil, &capturingBlobStorage{}, &recordingMessageRepository{})
+	uc.SetAuthenticator(auth)
+
+	in := inboundInput(1)
+	in.ClientIP = parseTestIP("192.0.2.10")
+	in.HeloDomain = "mx.sender.test"
+
+	if err := uc.Handle(context.Background(), in); err != nil {
+		t.Fatalf("Handle: %v", err)
+	}
+
+	if auth.seen.ClientIP.String() != "192.0.2.10" {
+		t.Errorf("ClientIP = %v, want 192.0.2.10", auth.seen.ClientIP)
+	}
+	if auth.seen.HeloDomain != "mx.sender.test" {
+		t.Errorf("HeloDomain = %q, want mx.sender.test", auth.seen.HeloDomain)
+	}
+	if auth.seen.EnvelopeFrom != "sender@sender.test" {
+		t.Errorf("EnvelopeFrom = %q", auth.seen.EnvelopeFrom)
+	}
+}
+
+func parseTestIP(s string) net.IP { return net.ParseIP(s) }

services/protocols/internal/application/usecase/inbound_scan_headers_test.go

@@ -0,0 +1,99 @@
+package usecase
+
+import (
+	"bytes"
+	"context"
+	"io"
+	"strings"
+	"testing"
+
+	"github.com/google/uuid"
+
+	"lambdamail/protocols/internal/application/port"
+	"lambdamail/protocols/internal/domain/valueobject"
+)
+
+type capturingBlobStorage struct {
+	stored []byte
+}
+
+func (c *capturingBlobStorage) Store(_ context.Context, r io.Reader) (port.BlobRef, error) {
+	b, err := io.ReadAll(r)
+	c.stored = b
+	return port.BlobRef{ID: uuid.New(), SizeBytes: int64(len(b))}, err
+}
+
+type stubScanner struct {
+	result *valueobject.ScanResult
+}
+
+func (s *stubScanner) Scan(_ context.Context, _ port.ScanInput) (*valueobject.ScanResult, error) {
+	return s.result, nil
+}
+
+// The scan verdict is only actionable by the user - and by their Sieve rules -
+// if it reaches the stored message. PLAN.md section 6.1 persists the EML
+// together with the verdicts, so the spam headers the scanner produced must be
+// present in the delivered message.
+func TestUseCase_Handle_WritesScanHeadersIntoStoredMessage(t *testing.T) {
+	blobs := &capturingBlobStorage{}
+	scanner := &stubScanner{result: &valueobject.ScanResult{
+		Verdict: valueobject.ScanVerdictSpamJunk,
+		Score:   9.5,
+		HeadersToAdd: map[string]string{
+			"X-Spam-Flag":  "YES",
+			"X-Spam-Score": "9.50",
+		},
+	}}
+
+	uc := NewProcessInboundEmailUseCase(nil, blobs, &recordingMessageRepository{})
+	uc.SetScanner(scanner)
+
+	err := uc.Handle(context.Background(), ProcessInboundEmailInput{
+		Sender:             "spammer@example.test",
+		Recipients:         []port.MailboxRecord{{ID: uuid.New()}},
+		RecipientAddresses: []string{"victim@example.test"},
+		Body:               bytes.NewBufferString("Subject: buy now\r\n\r\nbody"),
+	})
+	if err != nil {
+		t.Fatalf("Handle: %v", err)
+	}
+
+	stored := string(blobs.stored)
+	for _, want := range []string{"X-Spam-Flag: YES", "X-Spam-Score: 9.50"} {
+		if !strings.Contains(stored, want) {
+			t.Errorf("stored message is missing %q:\n%s", want, stored)
+		}
+	}
+	if !strings.Contains(stored, "Subject: buy now") {
+		t.Errorf("original headers were lost:\n%s", stored)
+	}
+	// Added headers must precede the original ones and stay inside the header
+	// block, i.e. before the first empty line.
+	headerBlock, _, found := strings.Cut(stored, "\r\n\r\n")
+	if !found {
+		t.Fatalf("stored message has no header/body separator:\n%s", stored)
+	}
+	if !strings.Contains(headerBlock, "X-Spam-Flag: YES") {
+		t.Errorf("scan headers leaked into the body:\n%s", stored)
+	}
+}
+
+func TestUseCase_Handle_LeavesMessageUntouchedWithoutScanHeaders(t *testing.T) {
+	blobs := &capturingBlobStorage{}
+	uc := NewProcessInboundEmailUseCase(nil, blobs, &recordingMessageRepository{})
+
+	original := "Subject: hi\r\n\r\nbody"
+	err := uc.Handle(context.Background(), ProcessInboundEmailInput{
+		Recipients:         []port.MailboxRecord{{ID: uuid.New()}},
+		RecipientAddresses: []string{"a@example.test"},
+		Body:               bytes.NewBufferString(original),
+	})
+	if err != nil {
+		t.Fatalf("Handle: %v", err)
+	}
+
+	if string(blobs.stored) != original {
+		t.Errorf("message was rewritten without a scanner: got %q, want %q", blobs.stored, original)
+	}
+}

services/protocols/internal/application/usecase/managesieve_session.go

@@ -12,10 +12,10 @@ import (
 )
 
 var (
-	ErrScriptNotFound       = errors.New("script does not exist")
-	ErrActiveScriptDelete   = errors.New("cannot delete active script")
+	ErrScriptNotFound      = errors.New("script does not exist")
+	ErrActiveScriptDelete  = errors.New("cannot delete active script")
 	ErrScriptAlreadyExists = errors.New("script with new name already exists")
-	ErrScriptQuotaExceeded  = errors.New("script size exceeds storage limit")
+	ErrScriptQuotaExceeded = errors.New("script size exceeds storage limit")
 )
 
 const MaxScriptSizeBytes = 1024 * 1024 // 1 MB limit per Sieve script

services/protocols/internal/application/usecase/managesieve_session_test.go

@@ -135,7 +135,7 @@ func TestManageSieveSessionUseCase_Put_Get_List_SetActive_Delete(t *testing.T) {
 		t.Fatalf("SetActive failed: %v", err)
 	}
 
-	// 6. Delete active script fails per RFC 5804 §2.7
+	// 6. Delete active script fails per RFC 5804 section 2.7
 	if err := uc.DeleteScript(ctx, gotID, "main_rules"); !errors.Is(err, ErrActiveScriptDelete) {
 		t.Fatalf("expected ErrActiveScriptDelete, got %v", err)
 	}

services/protocols/internal/application/usecase/outbound_dsn_test.go

@@ -0,0 +1,168 @@
+package usecase
+
+import (
+	"bufio"
+	"context"
+	"net"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/google/uuid"
+
+	"lambdamail/protocols/internal/application/port"
+	"lambdamail/protocols/internal/domain/entity"
+)
+
+// startFakeMX serves one SMTP conversation, answering MAIL FROM with the given
+// reply so the worker can be driven through a real permanent/temporary failure.
+func startFakeMX(t *testing.T, mailReply string) string {
+	t.Helper()
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("listen: %v", err)
+	}
+	t.Cleanup(func() { ln.Close() })
+
+	go func() {
+		for {
+			conn, err := ln.Accept()
+			if err != nil {
+				return
+			}
+			go func(c net.Conn) {
+				defer c.Close()
+				c.SetDeadline(time.Now().Add(5 * time.Second))
+				r := bufio.NewReader(c)
+				c.Write([]byte("220 fake.mx ESMTP\r\n"))
+				for {
+					line, err := r.ReadString('\n')
+					if err != nil {
+						return
+					}
+					cmd := strings.ToUpper(strings.TrimSpace(line))
+					switch {
+					case strings.HasPrefix(cmd, "EHLO"), strings.HasPrefix(cmd, "HELO"):
+						c.Write([]byte("250 fake.mx\r\n"))
+					case strings.HasPrefix(cmd, "MAIL FROM"):
+						c.Write([]byte(mailReply + "\r\n"))
+					case strings.HasPrefix(cmd, "QUIT"):
+						c.Write([]byte("221 Bye\r\n"))
+						return
+					default:
+						c.Write([]byte("250 Ok\r\n"))
+					}
+				}
+			}(conn)
+		}
+	}()
+
+	return ln.Addr().String()
+}
+
+func newTestJob() *entity.OutboundJob {
+	mbID := uuid.New()
+	return &entity.OutboundJob{
+		ID:                uuid.New(),
+		MailboxID:         &mbID,
+		BlobID:            uuid.New(),
+		EnvelopeFrom:      "user@domain.test",
+		EnvelopeTo:        "rcpt@remote.test",
+		DestinationDomain: "remote.test",
+		Status:            entity.OutboundJobStatusQueued,
+		ExpiresAt:         time.Now().Add(5 * 24 * time.Hour),
+	}
+}
+
+// PLAN.md section 6.3: a 5xx is a permanent failure and must bounce
+// immediately with a DSN, not sit in the queue retrying for five days.
+func TestOutboundWorker_PermanentSmtpFailureBouncesImmediately(t *testing.T) {
+	addr := startFakeMX(t, "550 5.1.1 User unknown")
+
+	repo := &fakeOutboundRepo{}
+	repo.Enqueue(context.Background(), newTestJob())
+
+	worker := NewOutboundWorkerUseCase(
+		repo,
+		&fakeMXResolver{hosts: []string{addr}},
+		&fakeBlobReader{payload: []byte("From: a\r\nTo: b\r\n\r\nTest")},
+		nil, nil, "mail.local",
+	)
+
+	if _, err := worker.ProcessBatch(context.Background(), "w1", 10); err != nil {
+		t.Fatalf("ProcessBatch: %v", err)
+	}
+
+	got := repo.jobs[0]
+	if got.Status != entity.OutboundJobStatusBounced {
+		t.Errorf("status = %s, want BOUNCED for a 5xx reply", got.Status)
+	}
+	if got.LastSmtpCode != "550" {
+		t.Errorf("LastSmtpCode = %q, want %q", got.LastSmtpCode, "550")
+	}
+}
+
+// A 4xx is temporary and must be deferred for a later retry.
+func TestOutboundWorker_TemporarySmtpFailureIsDeferred(t *testing.T) {
+	addr := startFakeMX(t, "451 4.3.0 Try later")
+
+	repo := &fakeOutboundRepo{}
+	repo.Enqueue(context.Background(), newTestJob())
+
+	worker := NewOutboundWorkerUseCase(
+		repo,
+		&fakeMXResolver{hosts: []string{addr}},
+		&fakeBlobReader{payload: []byte("From: a\r\nTo: b\r\n\r\nTest")},
+		nil, nil, "mail.local",
+	)
+
+	if _, err := worker.ProcessBatch(context.Background(), "w1", 10); err != nil {
+		t.Fatalf("ProcessBatch: %v", err)
+	}
+
+	got := repo.jobs[0]
+	if got.Status != entity.OutboundJobStatusDeferred {
+		t.Errorf("status = %s, want DEFERRED for a 4xx reply", got.Status)
+	}
+	if got.LastSmtpCode != "451" {
+		t.Errorf("LastSmtpCode = %q, want %q", got.LastSmtpCode, "451")
+	}
+}
+
+// The DSN is delivered back to the original sender. When that sender address is
+// an alias fanning out to several mailboxes, the recipient records and their
+// envelope addresses must stay aligned - otherwise the delivery indexes past
+// the end of the address list and takes the worker down.
+func TestOutboundWorker_DsnToFanOutSenderDeliversToEveryTarget(t *testing.T) {
+	addr := startFakeMX(t, "550 5.1.1 User unknown")
+
+	repo := &fakeOutboundRepo{}
+	repo.Enqueue(context.Background(), newTestJob())
+
+	mailboxes := &fakeAliasFanOutRepository{targets: []port.MailboxRecord{
+		{ID: uuid.New(), QuotaBytes: 1000},
+		{ID: uuid.New(), QuotaBytes: 1000},
+	}}
+	messages := &recordingMessageRepository{}
+	inbound := NewProcessInboundEmailUseCase(mailboxes, &stubBlobStorage{ref: port.BlobRef{ID: uuid.New()}}, messages)
+
+	worker := NewOutboundWorkerUseCase(
+		repo,
+		&fakeMXResolver{hosts: []string{addr}},
+		&fakeBlobReader{payload: []byte("From: a\r\nTo: b\r\n\r\nTest")},
+		inbound, mailboxes, "mail.local",
+	)
+
+	if _, err := worker.ProcessBatch(context.Background(), "w1", 10); err != nil {
+		t.Fatalf("ProcessBatch: %v", err)
+	}
+
+	if len(messages.persisted) != 2 {
+		t.Fatalf("DSN persisted to %d mailboxes, want 2 (one per fan-out target)", len(messages.persisted))
+	}
+	for i, p := range messages.persisted {
+		if p.RecipientAddress != "user@domain.test" {
+			t.Errorf("persisted[%d].RecipientAddress = %q, want the original sender", i, p.RecipientAddress)
+		}
+	}
+}

services/protocols/internal/application/usecase/outbound_tls_policy_test.go

@@ -0,0 +1,190 @@
+package usecase
+
+import (
+	"bufio"
+	"context"
+	"fmt"
+	"net"
+	"strings"
+	"testing"
+	"time"
+
+	"lambdamail/protocols/internal/domain/entity"
+)
+
+// startPlaintextMX serves an SMTP conversation that never offers STARTTLS,
+// which is what a downgrade attack looks like from our side.
+func startPlaintextMX(t *testing.T) string {
+	t.Helper()
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("listen: %v", err)
+	}
+	t.Cleanup(func() { ln.Close() })
+
+	go func() {
+		for {
+			conn, err := ln.Accept()
+			if err != nil {
+				return
+			}
+			go func(c net.Conn) {
+				defer c.Close()
+				c.SetDeadline(time.Now().Add(5 * time.Second))
+				r := bufio.NewReader(c)
+				c.Write([]byte("220 plain.mx ESMTP\r\n"))
+				for {
+					line, err := r.ReadString('\n')
+					if err != nil {
+						return
+					}
+					cmd := strings.ToUpper(strings.TrimSpace(line))
+					switch {
+					case strings.HasPrefix(cmd, "EHLO"):
+						// Deliberately no STARTTLS in the extension list.
+						c.Write([]byte("250-plain.mx\r\n250 SIZE 10240000\r\n"))
+					case cmd == "DATA":
+						c.Write([]byte("354 End data with <CR><LF>.<CR><LF>\r\n"))
+						for {
+							body, err := r.ReadString('\n')
+							if err != nil {
+								return
+							}
+							if strings.TrimSpace(body) == "." {
+								break
+							}
+						}
+						c.Write([]byte("250 2.0.0 Ok: queued\r\n"))
+					case strings.HasPrefix(cmd, "QUIT"):
+						c.Write([]byte("221 Bye\r\n"))
+						return
+					default:
+						c.Write([]byte("250 Ok\r\n"))
+					}
+				}
+			}(conn)
+		}
+	}()
+
+	return ln.Addr().String()
+}
+
+type stubPolicyResolver struct {
+	policy entity.TLSPolicy
+	err    error
+}
+
+func (s stubPolicyResolver) Resolve(_ context.Context, _ string, _ string) (entity.TLSPolicy, error) {
+	return s.policy, s.err
+}
+
+func runWorkerWithPolicy(t *testing.T, mxAddr string, resolver stubPolicyResolver) *entity.OutboundJob {
+	t.Helper()
+
+	repo := &fakeOutboundRepo{}
+	repo.Enqueue(context.Background(), newTestJob())
+
+	worker := NewOutboundWorkerUseCase(
+		repo,
+		&fakeMXResolver{hosts: []string{mxAddr}},
+		&fakeBlobReader{payload: []byte("From: a\r\nTo: b\r\n\r\nTest")},
+		nil, nil, "mail.local",
+	)
+	worker.SetPolicyResolver(resolver)
+
+	if _, err := worker.ProcessBatch(context.Background(), "w1", 10); err != nil {
+		t.Fatalf("ProcessBatch: %v", err)
+	}
+	return repo.jobs[0]
+}
+
+// PLAN.md section 6.2: when the destination's policy demands validated TLS
+// and it cannot be had, the message is deferred - never delivered in the
+// clear. This is the anti-downgrade guarantee.
+func TestOutboundWorker_DefersRatherThanDowngradeUnderEnforcePolicy(t *testing.T) {
+	addr := startPlaintextMX(t)
+
+	got := runWorkerWithPolicy(t, addr, stubPolicyResolver{
+		policy: entity.NewMtaStsPolicy([]string{"*"}, true),
+	})
+
+	if got.Status != entity.OutboundJobStatusDeferred {
+		t.Errorf("status = %s, want DEFERRED", got.Status)
+	}
+	if got.LastSmtpCode != "451" {
+		t.Errorf("LastSmtpCode = %q, want 451", got.LastSmtpCode)
+	}
+	if !strings.Contains(got.LastError, "4.7.5") {
+		t.Errorf("LastError should carry the 4.7.5 status: %q", got.LastError)
+	}
+	if got.TlsPolicyUsed != "none" {
+		t.Errorf("TlsPolicyUsed = %q, want none", got.TlsPolicyUsed)
+	}
+}
+
+// The same MX, with no policy published, is delivered to over plaintext:
+// refusing here would lose legitimate mail (RFC 7435).
+func TestOutboundWorker_DeliversOpportunisticallyWithoutPolicy(t *testing.T) {
+	addr := startPlaintextMX(t)
+
+	got := runWorkerWithPolicy(t, addr, stubPolicyResolver{
+		policy: entity.NewTLSPolicy(false, false),
+	})
+
+	if got.Status != entity.OutboundJobStatusDelivered {
+		t.Errorf("status = %s, want DELIVERED (last error: %s)", got.Status, got.LastError)
+	}
+	if got.TlsPolicyUsed != entity.TLSModeOpportunistic {
+		t.Errorf("TlsPolicyUsed = %q, want opportunistic", got.TlsPolicyUsed)
+	}
+}
+
+// An MX outside the policy's mx set must not be used at all
+// (RFC 8461 section 4.1).
+func TestOutboundWorker_RefusesMxOutsidePolicy(t *testing.T) {
+	addr := startPlaintextMX(t)
+
+	got := runWorkerWithPolicy(t, addr, stubPolicyResolver{
+		policy: entity.NewMtaStsPolicy([]string{"only.allowed.test"}, true),
+	})
+
+	if got.Status != entity.OutboundJobStatusDeferred {
+		t.Errorf("status = %s, want DEFERRED", got.Status)
+	}
+	if !strings.Contains(got.LastError, "not listed in the MTA-STS policy") {
+		t.Errorf("LastError = %q, want it to name the policy mismatch", got.LastError)
+	}
+}
+
+// A policy that exists but cannot be evaluated is a reason to wait, not to
+// downgrade.
+func TestOutboundWorker_DefersWhenPolicyCannotBeResolved(t *testing.T) {
+	addr := startPlaintextMX(t)
+
+	got := runWorkerWithPolicy(t, addr, stubPolicyResolver{
+		err: fmt.Errorf("TLSA records are not DNSSEC-validated"),
+	})
+
+	if got.Status != entity.OutboundJobStatusDeferred {
+		t.Errorf("status = %s, want DEFERRED", got.Status)
+	}
+	if !strings.Contains(got.LastError, "DNSSEC") {
+		t.Errorf("LastError = %q, want the resolution failure to be recorded", got.LastError)
+	}
+}
+
+// A testing-mode policy reports but must not block delivery.
+func TestOutboundWorker_TestingModePolicyStillDelivers(t *testing.T) {
+	addr := startPlaintextMX(t)
+
+	got := runWorkerWithPolicy(t, addr, stubPolicyResolver{
+		policy: entity.NewMtaStsPolicy([]string{"only.allowed.test"}, false),
+	})
+
+	if got.Status != entity.OutboundJobStatusDelivered {
+		t.Errorf("status = %s, want DELIVERED under mode: testing (last error: %s)", got.Status, got.LastError)
+	}
+	if got.TlsPolicyUsed != entity.TLSModeMtaSts {
+		t.Errorf("TlsPolicyUsed = %q, want mta-sts", got.TlsPolicyUsed)
+	}
+}

services/protocols/internal/application/usecase/outbound_worker.go

@@ -4,9 +4,13 @@ import (
 	"bytes"
 	"context"
 	"crypto/tls"
+	"crypto/x509"
+	"errors"
 	"fmt"
 	"net"
 	"net/smtp"
+	"net/textproto"
+	"strconv"
 	"strings"
 	"time"
 
@@ -15,13 +19,35 @@ import (
 	"lambdamail/protocols/internal/domain/valueobject"
 )
 
+// ErrPolicyDowngradeRefused is returned when a destination's published TLS
+// policy could not be satisfied. PLAN.md section 6.2 is explicit: the message
+// is deferred with 4.7.5, never delivered over an unvalidated channel.
+var ErrPolicyDowngradeRefused = errors.New("outbound: refusing to deliver without the TLS validation the destination requires")
+
 type OutboundWorkerUseCase struct {
-	outboundRepo port.OutboundRepository
-	mxResolver   port.MXResolver
-	blobReader   port.BlobReader
-	inboundUC    *ProcessInboundEmailUseCase
-	mailboxes    port.MailboxRepository
-	localHost    string
+	outboundRepo   port.OutboundRepository
+	mxResolver     port.MXResolver
+	blobReader     port.BlobReader
+	inboundUC      *ProcessInboundEmailUseCase
+	mailboxes      port.MailboxRepository
+	policyResolver port.TLSPolicyResolver
+	relay          RelayConfig
+	localHost      string
+}
+
+// SetRelay routes delivery through a smarthost (PLAN.md section 10.4). This is
+// the fallback for hosts whose provider blocks outbound port 25, and it
+// replaces MX resolution entirely: every message goes to the relay.
+func (w *OutboundWorkerUseCase) SetRelay(relay RelayConfig) {
+	w.relay = relay
+}
+
+// SetPolicyResolver enables DANE and MTA-STS on the delivery path. Without
+// one the worker falls back to opportunistic TLS, which is correct for a
+// destination that publishes no policy but must never be the choice for one
+// that does.
+func (w *OutboundWorkerUseCase) SetPolicyResolver(resolver port.TLSPolicyResolver) {
+	w.policyResolver = resolver
 }
 
 func NewOutboundWorkerUseCase(
@@ -72,6 +98,21 @@ func (w *OutboundWorkerUseCase) processSingleJob(ctx context.Context, job *entit
 		return
 	}
 
+	// With a smarthost every message goes to the relay regardless of
+	// destination, and the relay owns transport security from there on.
+	if w.relay.Configured() {
+		if err := w.deliverViaRelay(job.EnvelopeFrom, job.EnvelopeTo, payload); err != nil {
+			w.finishFailed(ctx, job, err)
+			return
+		}
+		job.Status = entity.OutboundJobStatusDelivered
+		job.LastError = ""
+		job.LastSmtpCode = ""
+		job.TlsPolicyUsed = entity.TLSModeRelay
+		_ = w.outboundRepo.UpdateJob(ctx, job)
+		return
+	}
+
 	mxHosts, err := w.mxResolver.LookupMX(ctx, job.DestinationDomain)
 	if err != nil || len(mxHosts) == 0 {
 		mxHosts = []string{job.DestinationDomain}
@@ -79,10 +120,28 @@ func (w *OutboundWorkerUseCase) processSingleJob(ctx context.Context, job *entit
 
 	var lastErr error
 	delivered := false
+	policyUsed := entity.TLSModeOpportunistic
 
 	for _, mxHost := range mxHosts {
-		if err := w.deliverToMX(ctx, mxHost, job.EnvelopeFrom, job.EnvelopeTo, payload); err == nil {
+		policy, err := w.resolvePolicy(ctx, job.DestinationDomain, mxHost)
+		if err != nil {
+			// A published policy we cannot evaluate is a reason to wait, not
+			// a reason to send in the clear.
+			lastErr = err
+			continue
+		}
+
+		// RFC 8461 section 4.1: a host outside the policy's mx set must not
+		// be used while that policy is in force.
+		if policy.RequiresValidation() && !policy.CoversHost(mxHost) {
+			lastErr = fmt.Errorf("%w: %s is not listed in the MTA-STS policy of %s",
+				ErrPolicyDowngradeRefused, mxHost, job.DestinationDomain)
+			continue
+		}
+
+		if err := w.deliverToMX(ctx, mxHost, job.EnvelopeFrom, job.EnvelopeTo, payload, policy); err == nil {
 			delivered = true
+			policyUsed = policy.Effective()
 			break
 		} else {
 			lastErr = err
@@ -92,18 +151,52 @@ func (w *OutboundWorkerUseCase) processSingleJob(ctx context.Context, job *entit
 	if delivered {
 		job.Status = entity.OutboundJobStatusDelivered
 		job.LastError = ""
-		job.TlsPolicyUsed = "opportunistic"
+		job.LastSmtpCode = ""
+		job.TlsPolicyUsed = policyUsed
 		_ = w.outboundRepo.UpdateJob(ctx, job)
 		return
 	}
 
+	w.finishFailed(ctx, job, lastErr)
+}
+
+// finishFailed classifies a delivery failure and records the outcome.
+func (w *OutboundWorkerUseCase) finishFailed(ctx context.Context, job *entity.OutboundJob, lastErr error) {
 	errStr := "delivery failed"
 	if lastErr != nil {
 		errStr = lastErr.Error()
 	}
 
-	isPermanent := strings.HasPrefix(errStr, "5")
-	w.handleFailure(ctx, job, errStr, isPermanent)
+	// The remote reply code decides the outcome (PLAN.md section 6.3): 5xx is
+	// a permanent failure that bounces now, anything else - including a dial
+	// or TLS error, which carries no reply code at all - is retried.
+	code := smtpReplyCode(lastErr)
+	if code > 0 {
+		job.LastSmtpCode = strconv.Itoa(code)
+	}
+
+	// A refused downgrade is always temporary: the destination may fix its
+	// certificate, and bouncing would hand the attacker the outcome they
+	// wanted (PLAN.md section 6.2).
+	if errors.Is(lastErr, ErrPolicyDowngradeRefused) {
+		job.LastSmtpCode = "451"
+		job.TlsPolicyUsed = "none"
+		w.handleFailure(ctx, job, "4.7.5 "+errStr, false)
+		return
+	}
+
+	w.handleFailure(ctx, job, errStr, code >= 500 && code < 600)
+}
+
+// smtpReplyCode extracts the reply code from an error returned by net/smtp,
+// which wraps remote replies in *textproto.Error. It returns 0 when the
+// failure happened before any reply was read.
+func smtpReplyCode(err error) int {
+	var protoErr *textproto.Error
+	if errors.As(err, &protoErr) {
+		return protoErr.Code
+	}
+	return 0
 }
 
 func (w *OutboundWorkerUseCase) handleFailure(ctx context.Context, job *entity.OutboundJob, errStr string, isPermanent bool) {
@@ -141,20 +234,87 @@ func (w *OutboundWorkerUseCase) sendDsn(ctx context.Context, action valueobject.
 		return
 	}
 
-	if w.mailboxes != nil {
-		targets, err := w.mailboxes.ResolveDeliveryTargets(ctx, job.EnvelopeFrom)
-		if err == nil && len(targets) > 0 {
-			_ = w.inboundUC.Handle(ctx, ProcessInboundEmailInput{
-				Sender:             "postmaster@lambdamail.local",
-				Recipients:         targets,
-				RecipientAddresses: []string{job.EnvelopeFrom},
-				Body:               bytes.NewReader(dsnBytes),
-			})
-		}
+	if w.mailboxes == nil {
+		return
 	}
+
+	targets, err := w.mailboxes.ResolveDeliveryTargets(ctx, job.EnvelopeFrom)
+	if err != nil || len(targets) == 0 {
+		return
+	}
+
+	// Handle indexes the two slices in lockstep, so the envelope address is
+	// repeated once per resolved mailbox. An alias sender fans out to several
+	// mailboxes under the same address.
+	addresses := make([]string, len(targets))
+	for i := range targets {
+		addresses[i] = job.EnvelopeFrom
+	}
+
+	_ = w.inboundUC.Handle(ctx, ProcessInboundEmailInput{
+		Sender:             "postmaster@lambdamail.local",
+		Recipients:         targets,
+		RecipientAddresses: addresses,
+		Body:               bytes.NewReader(dsnBytes),
+	})
 }
 
-func (w *OutboundWorkerUseCase) deliverToMX(ctx context.Context, mxHost string, from string, to string, payload []byte) error {
+// resolvePolicy asks the resolver what transport security the destination
+// requires. With no resolver configured every destination is opportunistic.
+func (w *OutboundWorkerUseCase) resolvePolicy(ctx context.Context, destinationDomain, mxHost string) (entity.TLSPolicy, error) {
+	if w.policyResolver == nil {
+		return entity.NewTLSPolicy(false, false), nil
+	}
+	return w.policyResolver.Resolve(ctx, destinationDomain, mxHost)
+}
+
+// tlsConfigFor turns a policy into a TLS configuration.
+//
+// Opportunistic delivery deliberately skips verification: RFC 7435 prefers an
+// unauthenticated encrypted channel to a cleartext one, and the alternative -
+// refusing every destination with a self-signed certificate - would lose
+// legitimate mail. When a policy is in force the verification is real, and a
+// failure surfaces as a refusal to deliver.
+func tlsConfigFor(mxHost string, policy entity.TLSPolicy) *tls.Config {
+	config := &tls.Config{
+		ServerName: strings.TrimSuffix(mxHost, "."),
+		MinVersion: tls.VersionTLS12,
+	}
+
+	if !policy.RequiresValidation() {
+		config.InsecureSkipVerify = true
+		return config
+	}
+
+	if policy.Effective() == entity.TLSModeDane {
+		// DANE authenticates the certificate directly against the
+		// DNSSEC-signed association, so the PKIX chain and the name are not
+		// what is being trusted (RFC 7672 section 3.1). Verification is done
+		// by hand below instead of by the standard chain builder.
+		config.InsecureSkipVerify = true
+		config.VerifyPeerCertificate = func(rawCerts [][]byte, _ [][]*x509.Certificate) error {
+			chain := make([]*x509.Certificate, 0, len(rawCerts))
+			for _, raw := range rawCerts {
+				cert, err := x509.ParseCertificate(raw)
+				if err != nil {
+					return fmt.Errorf("parse peer certificate: %w", err)
+				}
+				chain = append(chain, cert)
+			}
+			if !policy.MatchesCertificate(chain) {
+				return fmt.Errorf("%w: certificate of %s matches no TLSA record", ErrPolicyDowngradeRefused, mxHost)
+			}
+			return nil
+		}
+		return config
+	}
+
+	// MTA-STS in enforce mode requires a normal, publicly trusted PKIX
+	// validation against the MX name (RFC 8461 section 4.1).
+	return config
+}
+
+func (w *OutboundWorkerUseCase) deliverToMX(ctx context.Context, mxHost string, from string, to string, payload []byte, policy entity.TLSPolicy) error {
 	addr := mxHost
 	if _, _, err := net.SplitHostPort(mxHost); err != nil {
 		addr = net.JoinHostPort(mxHost, "25")
@@ -177,11 +337,20 @@ func (w *OutboundWorkerUseCase) deliverToMX(ctx context.Context, mxHost string,
 		return fmt.Errorf("EHLO failed: %w", err)
 	}
 
-	if ok, _ := client.Extension("STARTTLS"); ok {
-		config := &tls.Config{InsecureSkipVerify: true, ServerName: mxHost}
-		if err := client.StartTLS(config); err != nil {
+	starttlsOffered, _ := client.Extension("STARTTLS")
+	if starttlsOffered {
+		if err := client.StartTLS(tlsConfigFor(mxHost, policy)); err != nil {
+			if policy.RequiresValidation() {
+				return fmt.Errorf("%w: STARTTLS to %s failed validation: %v", ErrPolicyDowngradeRefused, mxHost, err)
+			}
 			return fmt.Errorf("STARTTLS failed: %w", err)
 		}
+	} else if policy.RequiresValidation() {
+		// The destination's own published policy says it speaks TLS. A peer
+		// that does not offer STARTTLS is either broken or being stripped,
+		// and handing it the message either way is exactly the downgrade the
+		// policy exists to prevent.
+		return fmt.Errorf("%w: %s did not offer STARTTLS", ErrPolicyDowngradeRefused, mxHost)
 	}
 
 	if err := client.Mail(from); err != nil {

services/protocols/internal/application/usecase/outbound_worker_test.go

@@ -30,6 +30,10 @@ func (f *fakeOutboundRepo) FetchNextReady(_ context.Context, _ string, _ int) ([
 	return ready, nil
 }
 
+func (f *fakeOutboundRepo) CountRecipientsSince(_ context.Context, _ uuid.UUID, _ time.Time) (int, error) {
+	return 0, nil
+}
+
 func (f *fakeOutboundRepo) UpdateJob(_ context.Context, job *entity.OutboundJob) error {
 	for i, j := range f.jobs {
 		if j.ID == job.ID {

services/protocols/internal/application/usecase/preflight.go

@@ -0,0 +1,404 @@
+package usecase
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"sort"
+	"strings"
+	"time"
+)
+
+// Severity mirrors the table in PLAN.md section 15.
+type Severity string
+
+const (
+	SeverityCritical Severity = "CRITICAL"
+	SeverityHigh     Severity = "HIGH"
+	SeverityMedium   Severity = "MEDIUM"
+)
+
+// CheckStatus is the outcome of one preflight check.
+type CheckStatus string
+
+const (
+	CheckPassed  CheckStatus = "PASS"
+	CheckFailed  CheckStatus = "FAIL"
+	CheckSkipped CheckStatus = "SKIP"
+)
+
+// CheckResult is one line of the preflight report.
+type CheckResult struct {
+	Name     string
+	Status   CheckStatus
+	Severity Severity
+	Detail   string
+	// Remedy is the operator action that fixes it. Several of these checks
+	// cover steps PLAN.md section 7.4 lists as not automatable, so telling
+	// the operator exactly what to do is the point of the check.
+	Remedy string
+}
+
+// PreflightReport aggregates the checks.
+type PreflightReport struct {
+	Results []CheckResult
+}
+
+// Blocking reports whether any critical check failed. PLAN.md section 15 uses
+// this to keep a domain out of the VERIFIED state.
+func (r PreflightReport) Blocking() bool {
+	for _, result := range r.Results {
+		if result.Status == CheckFailed && result.Severity == SeverityCritical {
+			return true
+		}
+	}
+	return false
+}
+
+func (r PreflightReport) String() string {
+	var sb strings.Builder
+	for _, result := range r.Results {
+		fmt.Fprintf(&sb, "[%-4s] %-10s %s", result.Status, result.Severity, result.Name)
+		if result.Detail != "" {
+			fmt.Fprintf(&sb, "\n           %s", result.Detail)
+		}
+		if result.Status == CheckFailed && result.Remedy != "" {
+			fmt.Fprintf(&sb, "\n           remedy: %s", result.Remedy)
+		}
+		sb.WriteString("\n")
+	}
+	return sb.String()
+}
+
+// PreflightDeps are the environment probes the checks need. They are injected
+// so the whole preflight is testable without touching the network.
+type PreflightDeps struct {
+	// DialPort25 reports whether outbound port 25 reaches a known MX.
+	DialPort25 func(ctx context.Context, address string) error
+	// LookupAddr resolves the PTR of an IP.
+	LookupAddr func(ctx context.Context, ip string) ([]string, error)
+	// LookupHost resolves a name to addresses.
+	LookupHost func(ctx context.Context, host string) ([]string, error)
+	// LookupTXT resolves TXT records, used for the DNSBL checks.
+	LookupTXT func(ctx context.Context, name string) ([]string, error)
+	// HasCertificateFor reports whether a certificate is loaded for a host.
+	HasCertificateFor func(host string) bool
+	// FetchMtaSts fetches the served MTA-STS policy over HTTPS.
+	FetchMtaSts func(ctx context.Context, domain string) error
+	// FreeDiskPercent reports the free space on the mail spool.
+	FreeDiskPercent func() (float64, error)
+	// Now is the local clock; drift against NTP breaks DKIM and TOTP.
+	Now func() time.Time
+	// NetworkTime returns a trusted time to compare the local clock against.
+	NetworkTime func(ctx context.Context) (time.Time, error)
+}
+
+// PreflightInput describes the deployment being checked.
+type PreflightInput struct {
+	PrimaryMailHost string
+	MailDomain      string
+	PublicIPv4      string
+	PublicIPv6      string
+	DaneEnabled     bool
+	TLSMode         string
+	SmarthostSet    bool
+}
+
+// PreflightUseCase implements PLAN.md section 15.
+type PreflightUseCase struct {
+	deps PreflightDeps
+}
+
+func NewPreflightUseCase(deps PreflightDeps) *PreflightUseCase {
+	return &PreflightUseCase{deps: deps}
+}
+
+// wellKnownMX is the probe target of PLAN.md section 15. Google is used
+// because it is the destination most likely to matter and least likely to be
+// down.
+const wellKnownMX = "gmail-smtp-in.l.google.com:25"
+
+// dnsblZones are the reputation lists PLAN.md section 5.2 names.
+var dnsblZones = map[string]string{
+	"zen.spamhaus.org":       "Spamhaus ZEN",
+	"b.barracudacentral.org": "Barracuda",
+	"dnsbl.sorbs.net":        "SORBS",
+}
+
+func (uc *PreflightUseCase) Execute(ctx context.Context, input PreflightInput) PreflightReport {
+	report := PreflightReport{}
+	add := func(r CheckResult) { report.Results = append(report.Results, r) }
+
+	add(uc.checkPort25(ctx, input))
+	add(uc.checkReverseDNS(ctx, input))
+	add(uc.checkForwardConfirmedReverseDNS(ctx, input))
+	add(uc.checkBlocklists(ctx, input))
+	add(uc.checkCertificate(input))
+	add(uc.checkDaneRequiresAcmeMode(input))
+	add(uc.checkMtaStsEndpoint(ctx, input))
+	add(uc.checkClockDrift(ctx))
+	add(uc.checkDiskSpace())
+	add(uc.checkIPv6Coherence(ctx, input))
+
+	return report
+}
+
+func (uc *PreflightUseCase) checkPort25(ctx context.Context, input PreflightInput) CheckResult {
+	const name = "Outbound port 25 reaches a public MX"
+
+	if input.SmarthostSet {
+		return CheckResult{
+			Name: name, Status: CheckSkipped, Severity: SeverityCritical,
+			Detail: "a smarthost is configured, so direct delivery on port 25 is not used",
+		}
+	}
+	if uc.deps.DialPort25 == nil {
+		return skipped(name, SeverityCritical)
+	}
+
+	if err := uc.deps.DialPort25(ctx, wellKnownMX); err != nil {
+		return CheckResult{
+			Name: name, Status: CheckFailed, Severity: SeverityCritical,
+			Detail: fmt.Sprintf("could not reach %s: %v", wellKnownMX, err),
+			Remedy: "most VPS providers block egress on port 25 by default; ask the provider to unblock it, or configure RELAY_HOST to deliver through a smarthost",
+		}
+	}
+	return passed(name, SeverityCritical, "")
+}
+
+func (uc *PreflightUseCase) checkReverseDNS(ctx context.Context, input PreflightInput) CheckResult {
+	const name = "PTR of the public IP resolves to the mail host"
+
+	if uc.deps.LookupAddr == nil || input.PublicIPv4 == "" {
+		return skipped(name, SeverityCritical)
+	}
+
+	names, err := uc.deps.LookupAddr(ctx, input.PublicIPv4)
+	if err != nil || len(names) == 0 {
+		return CheckResult{
+			Name: name, Status: CheckFailed, Severity: SeverityCritical,
+			Detail: fmt.Sprintf("no PTR record for %s", input.PublicIPv4),
+			Remedy: "set the PTR in the hosting provider's panel; reverse delegation belongs to the owner of the IP block, not to the DNS provider",
+		}
+	}
+
+	for _, candidate := range names {
+		if strings.EqualFold(strings.TrimSuffix(candidate, "."), input.PrimaryMailHost) {
+			return passed(name, SeverityCritical, "")
+		}
+	}
+
+	return CheckResult{
+		Name: name, Status: CheckFailed, Severity: SeverityCritical,
+		Detail: fmt.Sprintf("PTR of %s is %v, want %s", input.PublicIPv4, names, input.PrimaryMailHost),
+		Remedy: "point the PTR at " + input.PrimaryMailHost + " in the hosting provider's panel",
+	}
+}
+
+func (uc *PreflightUseCase) checkForwardConfirmedReverseDNS(ctx context.Context, input PreflightInput) CheckResult {
+	const name = "FCrDNS: the mail host resolves back to the public IP"
+
+	if uc.deps.LookupHost == nil || input.PublicIPv4 == "" {
+		return skipped(name, SeverityCritical)
+	}
+
+	addresses, err := uc.deps.LookupHost(ctx, input.PrimaryMailHost)
+	if err != nil {
+		return CheckResult{
+			Name: name, Status: CheckFailed, Severity: SeverityCritical,
+			Detail: fmt.Sprintf("cannot resolve %s: %v", input.PrimaryMailHost, err),
+			Remedy: "publish the A record for " + input.PrimaryMailHost,
+		}
+	}
+
+	for _, address := range addresses {
+		if address == input.PublicIPv4 {
+			return passed(name, SeverityCritical, "")
+		}
+	}
+
+	return CheckResult{
+		Name: name, Status: CheckFailed, Severity: SeverityCritical,
+		Detail: fmt.Sprintf("%s resolves to %v, not to %s", input.PrimaryMailHost, addresses, input.PublicIPv4),
+		Remedy: "make the A record and the PTR agree; Gmail and Outlook reject or spam-file mail without forward-confirmed reverse DNS",
+	}
+}
+
+func (uc *PreflightUseCase) checkBlocklists(ctx context.Context, input PreflightInput) CheckResult {
+	const name = "Public IP is not on a major blocklist"
+
+	if uc.deps.LookupTXT == nil || input.PublicIPv4 == "" {
+		return skipped(name, SeverityCritical)
+	}
+
+	reversed := reverseIPv4(input.PublicIPv4)
+	if reversed == "" {
+		return skipped(name, SeverityCritical)
+	}
+
+	var listed []string
+	// Sorted so the report is stable between runs.
+	zones := make([]string, 0, len(dnsblZones))
+	for zone := range dnsblZones {
+		zones = append(zones, zone)
+	}
+	sort.Strings(zones)
+
+	for _, zone := range zones {
+		if records, err := uc.deps.LookupTXT(ctx, reversed+"."+zone); err == nil && len(records) > 0 {
+			listed = append(listed, dnsblZones[zone])
+		}
+	}
+
+	if len(listed) > 0 {
+		return CheckResult{
+			Name: name, Status: CheckFailed, Severity: SeverityCritical,
+			Detail: fmt.Sprintf("%s is listed on: %s", input.PublicIPv4, strings.Join(listed, ", ")),
+			Remedy: "request delisting with each provider before sending, or move to an IP with clean reputation",
+		}
+	}
+	return passed(name, SeverityCritical, "")
+}
+
+func (uc *PreflightUseCase) checkCertificate(input PreflightInput) CheckResult {
+	const name = "A TLS certificate is loaded for the mail host"
+
+	if uc.deps.HasCertificateFor == nil {
+		return skipped(name, SeverityCritical)
+	}
+	if uc.deps.HasCertificateFor(input.PrimaryMailHost) {
+		return passed(name, SeverityCritical, "")
+	}
+
+	return CheckResult{
+		Name: name, Status: CheckFailed, Severity: SeverityCritical,
+		Detail: fmt.Sprintf("no certificate for %s", input.PrimaryMailHost),
+		Remedy: "Traefik only requests certificates for hosts it routes; declare an HTTP router with Host(`" + input.PrimaryMailHost + "`) so ACME issues one",
+	}
+}
+
+func (uc *PreflightUseCase) checkDaneRequiresAcmeMode(input PreflightInput) CheckResult {
+	const name = "DANE is only enabled in self-managed ACME mode"
+
+	if !input.DaneEnabled {
+		return CheckResult{
+			Name: name, Status: CheckSkipped, Severity: SeverityCritical,
+			Detail: "DANE is disabled",
+		}
+	}
+	if strings.EqualFold(input.TLSMode, "acme") {
+		return passed(name, SeverityCritical, "")
+	}
+
+	return CheckResult{
+		Name: name, Status: CheckFailed, Severity: SeverityCritical,
+		Detail: "DANE is enabled while certificates come from Traefik",
+		Remedy: "Traefik cannot sign a CSR with a pre-generated key, so the TLSA record would stop matching at the next renewal and every validating MTA would reject mail; set TLS_MODE=acme or disable DANE",
+	}
+}
+
+func (uc *PreflightUseCase) checkMtaStsEndpoint(ctx context.Context, input PreflightInput) CheckResult {
+	const name = "MTA-STS policy is served over HTTPS with a valid certificate"
+
+	if uc.deps.FetchMtaSts == nil || input.MailDomain == "" {
+		return skipped(name, SeverityHigh)
+	}
+	if err := uc.deps.FetchMtaSts(ctx, input.MailDomain); err != nil {
+		return CheckResult{
+			Name: name, Status: CheckFailed, Severity: SeverityHigh,
+			Detail: fmt.Sprintf("cannot fetch the policy for %s: %v", input.MailDomain, err),
+			Remedy: "publish the mta-sts host and route it through the proxy with a valid certificate; senders that cannot fetch the policy fall back to unprotected delivery",
+		}
+	}
+	return passed(name, SeverityHigh, "")
+}
+
+func (uc *PreflightUseCase) checkClockDrift(ctx context.Context) CheckResult {
+	const name = "System clock is synchronised"
+	const maxDrift = 5 * time.Second
+
+	if uc.deps.NetworkTime == nil || uc.deps.Now == nil {
+		return skipped(name, SeverityHigh)
+	}
+
+	networkTime, err := uc.deps.NetworkTime(ctx)
+	if err != nil {
+		return skipped(name, SeverityHigh)
+	}
+
+	drift := uc.deps.Now().Sub(networkTime)
+	if drift < 0 {
+		drift = -drift
+	}
+	if drift > maxDrift {
+		return CheckResult{
+			Name: name, Status: CheckFailed, Severity: SeverityHigh,
+			Detail: fmt.Sprintf("local clock is off by %v", drift.Round(time.Millisecond)),
+			Remedy: "enable NTP on the host; DKIM signature timestamps and TOTP codes both depend on an accurate clock",
+		}
+	}
+	return passed(name, SeverityHigh, fmt.Sprintf("drift %v", drift.Round(time.Millisecond)))
+}
+
+func (uc *PreflightUseCase) checkDiskSpace() CheckResult {
+	const name = "Mail spool has more than 20% free space"
+
+	if uc.deps.FreeDiskPercent == nil {
+		return skipped(name, SeverityMedium)
+	}
+
+	free, err := uc.deps.FreeDiskPercent()
+	if err != nil {
+		return skipped(name, SeverityMedium)
+	}
+	if free < 20 {
+		return CheckResult{
+			Name: name, Status: CheckFailed, Severity: SeverityMedium,
+			Detail: fmt.Sprintf("%.1f%% free", free),
+			Remedy: "free space or grow the volume; a full spool means accepted mail cannot be written and has to be refused",
+		}
+	}
+	return passed(name, SeverityMedium, fmt.Sprintf("%.1f%% free", free))
+}
+
+func (uc *PreflightUseCase) checkIPv6Coherence(ctx context.Context, input PreflightInput) CheckResult {
+	const name = "IPv6 is either fully configured or disabled"
+
+	if input.PublicIPv6 == "" {
+		return passed(name, SeverityMedium, "IPv6 is disabled")
+	}
+	if uc.deps.LookupAddr == nil {
+		return skipped(name, SeverityMedium)
+	}
+
+	names, err := uc.deps.LookupAddr(ctx, input.PublicIPv6)
+	if err != nil || len(names) == 0 {
+		return CheckResult{
+			Name: name, Status: CheckFailed, Severity: SeverityMedium,
+			Detail: fmt.Sprintf("no PTR for %s", input.PublicIPv6),
+			Remedy: "publish a PTR for the IPv6 address or unset PUBLIC_IPV6; half-configured IPv6 is a common cause of rejection",
+		}
+	}
+	return passed(name, SeverityMedium, "")
+}
+
+func passed(name string, severity Severity, detail string) CheckResult {
+	return CheckResult{Name: name, Status: CheckPassed, Severity: severity, Detail: detail}
+}
+
+func skipped(name string, severity Severity) CheckResult {
+	return CheckResult{
+		Name: name, Status: CheckSkipped, Severity: severity,
+		Detail: "not enough configuration to run this check",
+	}
+}
+
+// reverseIPv4 turns "192.0.2.10" into "10.2.0.192", the form DNSBL queries
+// take. It returns an empty string for anything that is not an IPv4 address.
+func reverseIPv4(address string) string {
+	ip := net.ParseIP(address).To4()
+	if ip == nil {
+		return ""
+	}
+	return fmt.Sprintf("%d.%d.%d.%d", ip[3], ip[2], ip[1], ip[0])
+}

services/protocols/internal/application/usecase/preflight_test.go

@@ -0,0 +1,266 @@
+package usecase
+
+import (
+	"context"
+	"errors"
+	"strings"
+	"testing"
+	"time"
+)
+
+// healthyDeps is a deployment where every probe succeeds; individual tests
+// break exactly one thing so the failure being asserted is unambiguous.
+func healthyDeps() PreflightDeps {
+	now := time.Date(2026, 7, 20, 10, 0, 0, 0, time.UTC)
+	return PreflightDeps{
+		DialPort25:        func(context.Context, string) error { return nil },
+		LookupAddr:        func(_ context.Context, _ string) ([]string, error) { return []string{"mail.example.test."}, nil },
+		LookupHost:        func(_ context.Context, _ string) ([]string, error) { return []string{"192.0.2.10"}, nil },
+		LookupTXT:         func(_ context.Context, _ string) ([]string, error) { return nil, errors.New("NXDOMAIN") },
+		HasCertificateFor: func(string) bool { return true },
+		FetchMtaSts:       func(context.Context, string) error { return nil },
+		FreeDiskPercent:   func() (float64, error) { return 65, nil },
+		Now:               func() time.Time { return now },
+		NetworkTime:       func(context.Context) (time.Time, error) { return now, nil },
+	}
+}
+
+func healthyInput() PreflightInput {
+	return PreflightInput{
+		PrimaryMailHost: "mail.example.test",
+		MailDomain:      "example.test",
+		PublicIPv4:      "192.0.2.10",
+		TLSMode:         "traefik",
+	}
+}
+
+func findCheck(t *testing.T, report PreflightReport, substring string) CheckResult {
+	t.Helper()
+	for _, result := range report.Results {
+		if strings.Contains(result.Name, substring) {
+			return result
+		}
+	}
+	t.Fatalf("no check matching %q in report:\n%s", substring, report)
+	return CheckResult{}
+}
+
+func TestPreflight_HealthyDeploymentDoesNotBlock(t *testing.T) {
+	report := NewPreflightUseCase(healthyDeps()).Execute(context.Background(), healthyInput())
+
+	if report.Blocking() {
+		t.Errorf("a healthy deployment was reported as blocking:\n%s", report)
+	}
+}
+
+// PLAN.md premise 1: without outbound port 25 there is no direct delivery.
+func TestPreflight_BlockedPort25IsCriticalAndSuggestsSmarthost(t *testing.T) {
+	deps := healthyDeps()
+	deps.DialPort25 = func(context.Context, string) error { return errors.New("connection timed out") }
+
+	report := NewPreflightUseCase(deps).Execute(context.Background(), healthyInput())
+	check := findCheck(t, report, "port 25")
+
+	if check.Status != CheckFailed || check.Severity != SeverityCritical {
+		t.Errorf("check = %+v, want a critical failure", check)
+	}
+	if !strings.Contains(check.Remedy, "smarthost") {
+		t.Errorf("remedy should point at the smarthost fallback: %q", check.Remedy)
+	}
+	if !report.Blocking() {
+		t.Error("a blocked port 25 must block")
+	}
+}
+
+// With a smarthost configured, direct port 25 delivery is not used, so the
+// check must not block the deployment.
+func TestPreflight_SmarthostSkipsPort25Check(t *testing.T) {
+	deps := healthyDeps()
+	deps.DialPort25 = func(context.Context, string) error { return errors.New("blocked") }
+
+	input := healthyInput()
+	input.SmarthostSet = true
+
+	report := NewPreflightUseCase(deps).Execute(context.Background(), input)
+
+	if findCheck(t, report, "port 25").Status != CheckSkipped {
+		t.Error("the port 25 check should be skipped when a smarthost is configured")
+	}
+	if report.Blocking() {
+		t.Errorf("a smarthost deployment was blocked:\n%s", report)
+	}
+}
+
+// PLAN.md premise 2: PTR delegation belongs to the hosting provider, so the
+// remedy has to say so.
+func TestPreflight_MissingPtrIsCriticalAndNamesTheProvider(t *testing.T) {
+	deps := healthyDeps()
+	deps.LookupAddr = func(context.Context, string) ([]string, error) { return nil, errors.New("NXDOMAIN") }
+
+	report := NewPreflightUseCase(deps).Execute(context.Background(), healthyInput())
+	check := findCheck(t, report, "PTR")
+
+	if check.Status != CheckFailed || check.Severity != SeverityCritical {
+		t.Errorf("check = %+v, want a critical failure", check)
+	}
+	if !strings.Contains(check.Remedy, "hosting provider") {
+		t.Errorf("remedy should name the hosting provider: %q", check.Remedy)
+	}
+}
+
+func TestPreflight_ForwardConfirmedReverseDnsMismatchIsCritical(t *testing.T) {
+	deps := healthyDeps()
+	deps.LookupHost = func(context.Context, string) ([]string, error) { return []string{"198.51.100.1"}, nil }
+
+	report := NewPreflightUseCase(deps).Execute(context.Background(), healthyInput())
+
+	if check := findCheck(t, report, "FCrDNS"); check.Status != CheckFailed {
+		t.Errorf("check = %+v, want a failure when the A record and the PTR disagree", check)
+	}
+}
+
+func TestPreflight_ListedIpIsCriticalAndNamesTheList(t *testing.T) {
+	deps := healthyDeps()
+	deps.LookupTXT = func(_ context.Context, name string) ([]string, error) {
+		if strings.Contains(name, "zen.spamhaus.org") {
+			return []string{"https://www.spamhaus.org/query/ip/192.0.2.10"}, nil
+		}
+		return nil, errors.New("NXDOMAIN")
+	}
+
+	report := NewPreflightUseCase(deps).Execute(context.Background(), healthyInput())
+	check := findCheck(t, report, "blocklist")
+
+	if check.Status != CheckFailed || check.Severity != SeverityCritical {
+		t.Errorf("check = %+v, want a critical failure", check)
+	}
+	if !strings.Contains(check.Detail, "Spamhaus") {
+		t.Errorf("detail should name the list: %q", check.Detail)
+	}
+}
+
+// PLAN.md section 8.2 trap 2: Traefik only holds certificates for hosts it
+// routes, so the remedy has to explain the missing router.
+func TestPreflight_MissingCertificateExplainsTheTraefikRouter(t *testing.T) {
+	deps := healthyDeps()
+	deps.HasCertificateFor = func(string) bool { return false }
+
+	report := NewPreflightUseCase(deps).Execute(context.Background(), healthyInput())
+	check := findCheck(t, report, "certificate is loaded")
+
+	if check.Status != CheckFailed || check.Severity != SeverityCritical {
+		t.Errorf("check = %+v, want a critical failure", check)
+	}
+	if !strings.Contains(check.Remedy, "router") {
+		t.Errorf("remedy should explain the missing router: %q", check.Remedy)
+	}
+}
+
+// PLAN.md section 5.1: enabling DANE under Traefik-managed certificates
+// guarantees breakage at the next renewal, so the preflight must refuse it.
+func TestPreflight_DaneUnderTraefikModeIsRefused(t *testing.T) {
+	input := healthyInput()
+	input.DaneEnabled = true
+	input.TLSMode = "traefik"
+
+	report := NewPreflightUseCase(healthyDeps()).Execute(context.Background(), input)
+	check := findCheck(t, report, "DANE")
+
+	if check.Status != CheckFailed || check.Severity != SeverityCritical {
+		t.Errorf("check = %+v, want a critical failure", check)
+	}
+	if !report.Blocking() {
+		t.Error("DANE under Traefik mode must block the deployment")
+	}
+}
+
+func TestPreflight_DaneUnderAcmeModePasses(t *testing.T) {
+	input := healthyInput()
+	input.DaneEnabled = true
+	input.TLSMode = "acme"
+
+	report := NewPreflightUseCase(healthyDeps()).Execute(context.Background(), input)
+
+	if check := findCheck(t, report, "DANE"); check.Status != CheckPassed {
+		t.Errorf("check = %+v, want a pass under TLS_MODE=acme", check)
+	}
+}
+
+// DKIM signatures and TOTP codes both break on a drifting clock, but neither
+// loses mail outright, so this is high rather than critical.
+func TestPreflight_ClockDriftIsHighNotCritical(t *testing.T) {
+	deps := healthyDeps()
+	local := time.Date(2026, 7, 20, 10, 0, 0, 0, time.UTC)
+	deps.Now = func() time.Time { return local.Add(90 * time.Second) }
+	deps.NetworkTime = func(context.Context) (time.Time, error) { return local, nil }
+
+	report := NewPreflightUseCase(deps).Execute(context.Background(), healthyInput())
+	check := findCheck(t, report, "clock")
+
+	if check.Status != CheckFailed || check.Severity != SeverityHigh {
+		t.Errorf("check = %+v, want a high-severity failure", check)
+	}
+	if report.Blocking() {
+		t.Error("clock drift alone must not block the deployment")
+	}
+}
+
+func TestPreflight_LowDiskIsMediumSeverity(t *testing.T) {
+	deps := healthyDeps()
+	deps.FreeDiskPercent = func() (float64, error) { return 4, nil }
+
+	report := NewPreflightUseCase(deps).Execute(context.Background(), healthyInput())
+	check := findCheck(t, report, "free space")
+
+	if check.Status != CheckFailed || check.Severity != SeverityMedium {
+		t.Errorf("check = %+v, want a medium-severity failure", check)
+	}
+}
+
+// PLAN.md premise 5: half-configured IPv6 is a common cause of rejection, and
+// disabling it is a valid answer.
+func TestPreflight_IPv6WithoutPtrFailsButDisabledIPv6Passes(t *testing.T) {
+	deps := healthyDeps()
+	deps.LookupAddr = func(_ context.Context, ip string) ([]string, error) {
+		if strings.Contains(ip, ":") {
+			return nil, errors.New("NXDOMAIN")
+		}
+		return []string{"mail.example.test."}, nil
+	}
+
+	withIPv6 := healthyInput()
+	withIPv6.PublicIPv6 = "2001:db8::1"
+
+	report := NewPreflightUseCase(deps).Execute(context.Background(), withIPv6)
+	if check := findCheck(t, report, "IPv6"); check.Status != CheckFailed {
+		t.Errorf("check = %+v, want a failure for IPv6 without a PTR", check)
+	}
+
+	report = NewPreflightUseCase(deps).Execute(context.Background(), healthyInput())
+	if check := findCheck(t, report, "IPv6"); check.Status != CheckPassed {
+		t.Errorf("check = %+v, want a pass when IPv6 is disabled", check)
+	}
+}
+
+// A probe that cannot run is reported as skipped, never silently as a pass.
+func TestPreflight_MissingProbesAreSkippedNotPassed(t *testing.T) {
+	report := NewPreflightUseCase(PreflightDeps{}).Execute(context.Background(), healthyInput())
+
+	for _, result := range report.Results {
+		if result.Status == CheckPassed && result.Name != "IPv6 is either fully configured or disabled" {
+			t.Errorf("check %q passed with no probe configured", result.Name)
+		}
+	}
+	if report.Blocking() {
+		t.Error("skipped checks must not block")
+	}
+}
+
+func TestReverseIPv4(t *testing.T) {
+	if got := reverseIPv4("192.0.2.10"); got != "10.2.0.192" {
+		t.Errorf("reverseIPv4 = %q, want 10.2.0.192", got)
+	}
+	if got := reverseIPv4("2001:db8::1"); got != "" {
+		t.Errorf("reverseIPv4 of an IPv6 address = %q, want empty", got)
+	}
+}

services/protocols/internal/application/usecase/process_inbound_email.go

@@ -6,7 +6,11 @@ import (
 	"bytes"
 	"context"
 	"errors"
+	"fmt"
 	"io"
+	"log"
+	"net"
+	"sort"
 
 	"lambdamail/protocols/internal/application/port"
 	"lambdamail/protocols/internal/domain/valueobject"
@@ -31,6 +35,11 @@ type ProcessInboundEmailInput struct {
 	Recipients         []port.MailboxRecord
 	RecipientAddresses []string
 	Body               io.Reader
+	// ClientIP and HeloDomain identify the peer. SPF is defined over them
+	// (RFC 7208 section 2.3), so a delivery without them can only ever
+	// produce a "none" verdict.
+	ClientIP   net.IP
+	HeloDomain string
 }
 
 // ProcessInboundEmailUseCase implements the inbound half of PLAN.md section
@@ -39,6 +48,8 @@ type ProcessInboundEmailInput struct {
 // later sub-projects).
 type ProcessInboundEmailUseCase struct {
 	scanner        port.ContentScanner
+	authenticator  port.MailAuthenticator
+	arcSealer      port.ArcSealer
 	mailboxes      port.MailboxRepository
 	blobs          port.BlobStorage
 	messages       port.InboundMessageRepository
@@ -54,11 +65,49 @@ func (uc *ProcessInboundEmailUseCase) SetScanner(scanner port.ContentScanner) {
 	uc.scanner = scanner
 }
 
+func (uc *ProcessInboundEmailUseCase) SetAuthenticator(authenticator port.MailAuthenticator) {
+	uc.authenticator = authenticator
+}
+
+// SetArcSealer enables ARC sealing of accepted messages. It is only worth
+// enabling on a host that forwards mail onward (PLAN.md section 5).
+func (uc *ProcessInboundEmailUseCase) SetArcSealer(sealer port.ArcSealer) {
+	uc.arcSealer = sealer
+}
+
 func (uc *ProcessInboundEmailUseCase) SetTrackerManager(tm *MailboxTrackerManager, folders port.ImapFolderRepository) {
 	uc.trackerManager = tm
 	uc.folders = folders
 }
 
+// prependHeaders inserts the scanner's verdict headers at the top of the
+// message. A receiving MTA adds its trace headers above the existing ones
+// (RFC 5321 section 4.4), which also keeps the original bytes - and therefore
+// any DKIM signature over them - untouched.
+func prependHeaders(payload []byte, headers map[string]string) []byte {
+	if len(headers) == 0 {
+		return payload
+	}
+
+	// Sorted so the delivered message is byte-for-byte reproducible instead of
+	// depending on Go's randomized map iteration order.
+	names := make([]string, 0, len(headers))
+	for name := range headers {
+		names = append(names, name)
+	}
+	sort.Strings(names)
+
+	var buf bytes.Buffer
+	for _, name := range names {
+		buf.WriteString(name)
+		buf.WriteString(": ")
+		buf.WriteString(headers[name])
+		buf.WriteString("\r\n")
+	}
+	buf.Write(payload)
+	return buf.Bytes()
+}
+
 // ResolveRecipient is called from the SMTP session's RCPT TO handler. It
 // returns every mailbox address should be delivered to (more than one for
 // an alias that fans out), or ErrRecipientNotFound / ErrMailboxQuotaExceeded.
@@ -84,12 +133,68 @@ func (uc *ProcessInboundEmailUseCase) ResolveRecipient(ctx context.Context, addr
 // the same blob (PLAN.md section 9's dedup design: 1 email to 50
 // recipients = 1 file).
 func (uc *ProcessInboundEmailUseCase) Handle(ctx context.Context, input ProcessInboundEmailInput) error {
+	// The two slices are indexed in lockstep below: one envelope address per
+	// resolved mailbox, repeated when an alias fans out. Refusing a mismatch
+	// turns a caller's bug into an error instead of an out-of-range panic that
+	// would take down the calling worker.
+	if len(input.Recipients) != len(input.RecipientAddresses) {
+		return fmt.Errorf(
+			"process inbound email: %d recipients but %d envelope addresses",
+			len(input.Recipients), len(input.RecipientAddresses),
+		)
+	}
+
 	payload, err := io.ReadAll(input.Body)
 	if err != nil {
 		return err
 	}
 
 	targetFolder := "INBOX"
+	authResult := port.InboundAuthResult{
+		SPF:   port.AuthResultNone,
+		DKIM:  port.AuthResultNone,
+		DMARC: port.AuthResultNone,
+	}
+
+	// Authentication runs before the content scanners so that the spam filter
+	// sees our Authentication-Results header and can score on it
+	// (PLAN.md section 6.1).
+	if uc.authenticator != nil {
+		authResult = uc.authenticator.Authenticate(ctx, port.InboundAuthInput{
+			ClientIP:     input.ClientIP,
+			HeloDomain:   input.HeloDomain,
+			EnvelopeFrom: input.Sender,
+			Message:      payload,
+		})
+
+		// Honouring a published "p=reject" is the whole point of the sender
+		// having published it. Quarantine is left to the spam filter, which
+		// files rather than refuses.
+		if authResult.DMARC == port.AuthResultFail && authResult.DmarcPolicy == "reject" {
+			return errors.New("550 5.7.1 DMARC policy rejects this message")
+		}
+
+		if authResult.AuthenticationResults != "" {
+			payload = prependHeaders(payload, map[string]string{
+				"Authentication-Results": authResult.AuthenticationResults,
+			})
+		}
+
+		// The ARC set has to be built over the message as it arrived, with
+		// this hop's verdict already known, so it is sealed here rather than
+		// after the content scanners rewrite headers.
+		if uc.arcSealer != nil {
+			sealed, err := uc.arcSealer.Seal(ctx, payload, authResult)
+			if err != nil {
+				// A sealing failure must not lose the message: it is delivered
+				// without the ARC set, which is exactly the state it would
+				// have been in had sealing not been enabled.
+				log.Printf("arc: could not seal message from %s: %v", input.Sender, err)
+			} else {
+				payload = sealed
+			}
+		}
+	}
 
 	if uc.scanner != nil {
 		recipientAddr := ""
@@ -115,6 +220,7 @@ func (uc *ProcessInboundEmailUseCase) Handle(ctx context.Context, input ProcessI
 			case valueobject.ScanVerdictSpamJunk:
 				targetFolder = "Junk"
 			}
+			payload = prependHeaders(payload, scanRes.HeadersToAdd)
 		}
 	}
 
@@ -130,9 +236,9 @@ func (uc *ProcessInboundEmailUseCase) Handle(ctx context.Context, input ProcessI
 			SenderAddress:    input.Sender,
 			RecipientAddress: input.RecipientAddresses[i],
 			TargetFolderName: targetFolder,
-			SPFResult:        "none",
-			DKIMResult:       "none",
-			DMARCResult:      "none",
+			SPFResult:        authResult.SPF,
+			DKIMResult:       authResult.DKIM,
+			DMARCResult:      authResult.DMARC,
 		})
 		if err != nil {
 			return err

services/protocols/internal/application/usecase/sync_dns_conflict_test.go

@@ -0,0 +1,179 @@
+package usecase
+
+import (
+	"context"
+	"strings"
+	"testing"
+
+	"lambdamail/protocols/internal/domain/entity"
+)
+
+func conflictTestInput() SyncDnsRecordsInput {
+	return SyncDnsRecordsInput{
+		DomainName:    "example.test",
+		MailHost:      "mail.example.test",
+		ServerIPv4:    "192.0.2.1",
+		RsaDkimPubKey: "rsaKey",
+		EdDkimPubKey:  "edKey",
+	}
+}
+
+// PLAN.md section 7.5: pre-existing records that are not ours are never
+// touched, only reported as conflicts. A third-party verification TXT sits at
+// the zone apex under the same type and name as our SPF record, so a reconciler
+// keyed only on type+name would overwrite it and break the other service.
+func TestSyncDnsRecords_ForeignApexTxtIsPreserved(t *testing.T) {
+	dns := newFakeDnsProvider()
+	dns.seed(entity.DnsRecord{
+		Type:  "TXT",
+		Name:  "example.test",
+		Value: "google-site-verification=abc123",
+	})
+
+	uc := NewSyncDnsRecordsUseCase(dns, nil)
+	out, err := uc.Execute(context.Background(), conflictTestInput())
+	if err != nil {
+		t.Fatalf("Execute: %v", err)
+	}
+
+	apexTxt := dns.find("TXT", "example.test")
+	if len(apexTxt) != 2 {
+		t.Fatalf("expected the foreign TXT and our SPF to coexist, got %d records", len(apexTxt))
+	}
+
+	var foundForeign, foundSPF bool
+	for _, r := range apexTxt {
+		if r.Value == "google-site-verification=abc123" {
+			foundForeign = true
+		}
+		if strings.HasPrefix(r.Value, "v=spf1") {
+			foundSPF = true
+		}
+	}
+	if !foundForeign {
+		t.Error("the foreign verification TXT was destroyed")
+	}
+	if !foundSPF {
+		t.Error("the SPF record was not created alongside the foreign apex TXT")
+	}
+	if out.ConflictCount != 0 {
+		t.Errorf("a coexisting foreign TXT is not a conflict, got ConflictCount=%d", out.ConflictCount)
+	}
+}
+
+// A name that admits only one value (the mail host A record) already pointing
+// somewhere else is a genuine conflict: silently repointing it could take down
+// an unrelated service.
+func TestSyncDnsRecords_ForeignARecordIsReportedAsConflict(t *testing.T) {
+	dns := newFakeDnsProvider()
+	dns.seed(entity.DnsRecord{
+		Type:    "A",
+		Name:    "mail.example.test",
+		Value:   "198.51.100.9",
+		Comment: "managed by something else",
+	})
+
+	uc := NewSyncDnsRecordsUseCase(dns, nil)
+	out, err := uc.Execute(context.Background(), conflictTestInput())
+	if err != nil {
+		t.Fatalf("Execute: %v", err)
+	}
+
+	records := dns.find("A", "mail.example.test")
+	if len(records) != 1 || records[0].Value != "198.51.100.9" {
+		t.Errorf("foreign A record was not left untouched: %+v", records)
+	}
+	if out.ConflictCount != 1 {
+		t.Fatalf("ConflictCount = %d, want 1", out.ConflictCount)
+	}
+	if out.Status != SyncStatusPartial {
+		t.Errorf("Status = %s, want %s", out.Status, SyncStatusPartial)
+	}
+	if !strings.Contains(out.Conflicts[0].String(), "198.51.100.9") {
+		t.Errorf("conflict report does not name the blocking value: %s", out.Conflicts[0])
+	}
+}
+
+// Our own records must still be updated in place when they drift.
+func TestSyncDnsRecords_OwnRecordDriftIsCorrected(t *testing.T) {
+	dns := newFakeDnsProvider()
+	uc := NewSyncDnsRecordsUseCase(dns, nil)
+	ctx := context.Background()
+
+	if _, err := uc.Execute(ctx, conflictTestInput()); err != nil {
+		t.Fatalf("initial Execute: %v", err)
+	}
+
+	for i, r := range dns.records {
+		if r.Type == "A" && r.Name == "mail.example.test" {
+			dns.records[i].Value = "203.0.113.7"
+		}
+	}
+
+	out, err := uc.Execute(ctx, conflictTestInput())
+	if err != nil {
+		t.Fatalf("second Execute: %v", err)
+	}
+
+	if out.UpdatedCount != 1 || out.ConflictCount != 0 {
+		t.Errorf("updated=%d conflicts=%d, want updated=1 conflicts=0", out.UpdatedCount, out.ConflictCount)
+	}
+	if records := dns.find("A", "mail.example.test"); records[0].Value != "192.0.2.1" {
+		t.Errorf("drifted A record was not corrected: got %q", records[0].Value)
+	}
+	if out.Status != SyncStatusVerified {
+		t.Errorf("Status = %s, want %s", out.Status, SyncStatusVerified)
+	}
+}
+
+type stubDnsVerifier struct {
+	invisible map[string]bool
+}
+
+func (s stubDnsVerifier) VerifyRecord(_ context.Context, record entity.DnsRecord) (bool, string) {
+	if s.invisible[record.Name] {
+		return false, "no answer"
+	}
+	return true, ""
+}
+
+// PLAN.md section 7.5 verifies through public resolvers after writing. A
+// record the provider accepted but nobody can resolve is drift, not success.
+func TestSyncDnsRecords_UnresolvableRecordIsReportedAsDrift(t *testing.T) {
+	dns := newFakeDnsProvider()
+	uc := NewSyncDnsRecordsUseCase(dns, nil)
+	uc.SetVerifier(stubDnsVerifier{invisible: map[string]bool{"mail.example.test": true}})
+
+	out, err := uc.Execute(context.Background(), conflictTestInput())
+	if err != nil {
+		t.Fatalf("Execute: %v", err)
+	}
+
+	if out.Status != SyncStatusDrift {
+		t.Errorf("Status = %s, want DRIFT", out.Status)
+	}
+	if len(out.Unverified) == 0 {
+		t.Fatal("the unresolvable record was not reported")
+	}
+	if !strings.Contains(out.Unverified[0], "mail.example.test") {
+		t.Errorf("Unverified = %v, want it to name the record", out.Unverified)
+	}
+}
+
+func TestSyncDnsRecords_AllRecordsVisibleIsVerified(t *testing.T) {
+	dns := newFakeDnsProvider()
+	uc := NewSyncDnsRecordsUseCase(dns, nil)
+	uc.SetVerifier(stubDnsVerifier{})
+
+	out, err := uc.Execute(context.Background(), conflictTestInput())
+	if err != nil {
+		t.Fatalf("Execute: %v", err)
+	}
+
+	if out.Status != SyncStatusVerified {
+		t.Errorf("Status = %s, want VERIFIED", out.Status)
+	}
+	if len(out.Unverified) != 0 {
+		t.Errorf("Unverified = %v, want empty", out.Unverified)
+	}
+}

services/protocols/internal/application/usecase/sync_dns_records.go

@@ -9,28 +9,68 @@ import (
 	"lambdamail/protocols/internal/domain/entity"
 )
 
+// SyncStatus is the outcome reported to the admin console (PLAN.md section 7.5).
+type SyncStatus string
+
+const (
+	SyncStatusVerified SyncStatus = "VERIFIED"
+	SyncStatusPartial  SyncStatus = "PARTIAL"
+	SyncStatusDrift    SyncStatus = "DRIFT"
+)
+
+// ownedRecordCommentPrefix marks the records this reconciler manages. Anything
+// in the zone without it that would collide with a desired record belongs to
+// somebody else and is reported instead of overwritten.
+const ownedRecordCommentPrefix = "LambdaMail"
+
 type SyncDnsRecordsInput struct {
-	DomainName        string
-	MailHost          string
-	ServerIPv4        string
-	ServerIPv6        string
-	RsaDkimPubKey     string
-	EdDkimPubKey      string
+	DomainName    string
+	MailHost      string
+	ServerIPv4    string
+	ServerIPv6    string
+	RsaDkimPubKey string
+	EdDkimPubKey  string
+	// TlsaHash publishes a single DANE association. TlsaHashes supersedes it
+	// and is what a rollover uses, since it can carry the current and the
+	// next key at once.
 	TlsaHash          string
+	TlsaHashes        []string
 	DaneEnabled       bool
+	RelaySpfInclude   string
 	AdminEmailAddress string
 }
 
+// SyncConflict describes a record that could not be reconciled because a
+// foreign record already occupies its name.
+type SyncConflict struct {
+	Type     string
+	Name     string
+	Existing string
+	Desired  string
+}
+
+func (c SyncConflict) String() string {
+	return fmt.Sprintf("%s %s: existing %q blocks desired %q", c.Type, c.Name, c.Existing, c.Desired)
+}
+
 type SyncDnsRecordsOutput struct {
 	ZoneID         string
+	Status         SyncStatus
 	CreatedCount   int
 	UpdatedCount   int
 	UnchangedCount int
+	ConflictCount  int
+	Conflicts      []SyncConflict
+	Errors         []string
+	// Unverified lists records that were written but could not be read back
+	// through the public resolvers.
+	Unverified []string
 }
 
 type SyncDnsRecordsUseCase struct {
 	dnsProvider port.DnsProvider
 	aliasRepo   port.SystemAliasRepository
+	verifier    port.DnsVerifier
 }
 
 func NewSyncDnsRecordsUseCase(dnsProvider port.DnsProvider, aliasRepo port.SystemAliasRepository) *SyncDnsRecordsUseCase {
@@ -40,21 +80,35 @@ func NewSyncDnsRecordsUseCase(dnsProvider port.DnsProvider, aliasRepo port.Syste
 	}
 }
 
+// SetVerifier enables the independent check of PLAN.md section 7.5: after
+// writing, the records are read back through public resolvers. The provider
+// accepting a write only proves the API accepted it, not that the record
+// resolves for anyone else.
+func (uc *SyncDnsRecordsUseCase) SetVerifier(verifier port.DnsVerifier) {
+	uc.verifier = verifier
+}
+
 func (uc *SyncDnsRecordsUseCase) Execute(ctx context.Context, input SyncDnsRecordsInput) (*SyncDnsRecordsOutput, error) {
 	if input.DomainName == "" {
 		return nil, fmt.Errorf("domain name is required")
 	}
 
-	desiredSpecs := entity.Build13DnsRecordSpecs(
-		input.DomainName,
-		input.MailHost,
-		input.ServerIPv4,
-		input.ServerIPv6,
-		input.RsaDkimPubKey,
-		input.EdDkimPubKey,
-		input.TlsaHash,
-		input.DaneEnabled,
-	)
+	tlsaHashes := input.TlsaHashes
+	if len(tlsaHashes) == 0 && input.TlsaHash != "" {
+		tlsaHashes = []string{input.TlsaHash}
+	}
+
+	desiredSpecs := entity.BuildDnsRecordSpecs(entity.DnsRecordSpec{
+		DomainName:      input.DomainName,
+		MailHost:        input.MailHost,
+		ServerIPv4:      input.ServerIPv4,
+		ServerIPv6:      input.ServerIPv6,
+		RsaDkimPubKey:   input.RsaDkimPubKey,
+		EdDkimPubKey:    input.EdDkimPubKey,
+		TlsaHashes:      tlsaHashes,
+		DaneEnabled:     input.DaneEnabled,
+		RelaySpfInclude: input.RelaySpfInclude,
+	})
 
 	zoneID, err := uc.dnsProvider.GetZoneID(ctx, input.DomainName)
 	if err != nil {
@@ -66,31 +120,48 @@ func (uc *SyncDnsRecordsUseCase) Execute(ctx context.Context, input SyncDnsRecor
 		return nil, fmt.Errorf("list dns records for zone %s: %w", zoneID, err)
 	}
 
-	existingMap := make(map[string]entity.DnsRecord)
+	// A single type+name can legitimately hold several records (multiple TXT at
+	// the zone apex is the common case), so the index maps to every candidate.
+	existingByKey := make(map[string][]entity.DnsRecord)
 	for _, rec := range existingRecords {
-		key := fmt.Sprintf("%s:%s", strings.ToUpper(rec.Type), strings.ToLower(rec.Name))
-		existingMap[key] = rec
+		key := recordKey(rec.Type, rec.Name)
+		existingByKey[key] = append(existingByKey[key], rec)
 	}
 
 	output := &SyncDnsRecordsOutput{ZoneID: zoneID}
 
 	for _, spec := range desiredSpecs {
-		key := fmt.Sprintf("%s:%s", strings.ToUpper(spec.Type), strings.ToLower(spec.Name))
-		existing, found := existingMap[key]
+		candidates := existingByKey[recordKey(spec.Type, spec.Name)]
+		match, foreign := classifyCandidates(spec, candidates)
 
-		if !found {
-			if err := uc.dnsProvider.CreateRecord(ctx, zoneID, spec); err != nil {
-				return nil, fmt.Errorf("create dns record %s %s: %w", spec.Type, spec.Name, err)
+		switch {
+		case match != nil:
+			if spec.EqualsNormalized(*match) {
+				output.UnchangedCount++
+				continue
 			}
-			output.CreatedCount++
-		} else if !spec.EqualsNormalized(existing) {
-			spec.ID = existing.ID
+			spec.ID = match.ID
 			if err := uc.dnsProvider.UpdateRecord(ctx, zoneID, spec); err != nil {
-				return nil, fmt.Errorf("update dns record %s %s: %w", spec.Type, spec.Name, err)
+				output.Errors = append(output.Errors, fmt.Sprintf("update %s %s: %v", spec.Type, spec.Name, err))
+				continue
 			}
 			output.UpdatedCount++
-		} else {
-			output.UnchangedCount++
+
+		case foreign != nil:
+			output.ConflictCount++
+			output.Conflicts = append(output.Conflicts, SyncConflict{
+				Type:     spec.Type,
+				Name:     spec.Name,
+				Existing: foreign.Value,
+				Desired:  spec.Value,
+			})
+
+		default:
+			if err := uc.dnsProvider.CreateRecord(ctx, zoneID, spec); err != nil {
+				output.Errors = append(output.Errors, fmt.Sprintf("create %s %s: %v", spec.Type, spec.Name, err))
+				continue
+			}
+			output.CreatedCount++
 		}
 	}
 
@@ -100,5 +171,104 @@ func (uc *SyncDnsRecordsUseCase) Execute(ctx context.Context, input SyncDnsRecor
 		}
 	}
 
+	output.Unverified = uc.verifyPublished(ctx, desiredSpecs)
+
+	output.Status = SyncStatusVerified
+	switch {
+	case output.ConflictCount > 0 || len(output.Errors) > 0:
+		output.Status = SyncStatusPartial
+	case len(output.Unverified) > 0:
+		// The records were written but the world cannot see them yet. That is
+		// drift, not success: reporting VERIFIED here is what would let a
+		// broken zone look healthy.
+		output.Status = SyncStatusDrift
+	}
+
 	return output, nil
 }
+
+// verifyPublished re-reads every desired record through public resolvers and
+// returns the ones that did not check out.
+func (uc *SyncDnsRecordsUseCase) verifyPublished(ctx context.Context, specs []entity.DnsRecord) []string {
+	if uc.verifier == nil {
+		return nil
+	}
+
+	var unverified []string
+	for _, spec := range specs {
+		visible, detail := uc.verifier.VerifyRecord(ctx, spec)
+		if visible {
+			continue
+		}
+		entry := fmt.Sprintf("%s %s", spec.Type, spec.Name)
+		if detail != "" {
+			entry += ": " + detail
+		}
+		unverified = append(unverified, entry)
+	}
+	return unverified
+}
+
+func recordKey(recType, name string) string {
+	return strings.ToUpper(recType) + ":" + strings.ToLower(strings.TrimSuffix(name, "."))
+}
+
+// classifyCandidates picks, among the records already published under a
+// desired record's type and name, the one this reconciler owns. It returns
+// either that match, or - when no record is ours and the name admits only a
+// single value - the foreign record blocking it.
+func classifyCandidates(spec entity.DnsRecord, candidates []entity.DnsRecord) (match *entity.DnsRecord, blocking *entity.DnsRecord) {
+	for i := range candidates {
+		if isOurRecord(spec, candidates[i]) {
+			return &candidates[i], nil
+		}
+	}
+	if len(candidates) > 0 && !allowsCoexistence(spec.Type) {
+		return nil, &candidates[0]
+	}
+	return nil, nil
+}
+
+// isOurRecord decides ownership. The record comment is the primary marker, but
+// it is not preserved by every provider or migration path, so TXT records fall
+// back to their protocol tag: only one "v=spf1" record may exist per name, so a
+// record carrying our tag is unambiguously the one we manage.
+func isOurRecord(spec, existing entity.DnsRecord) bool {
+	if strings.HasPrefix(existing.Comment, ownedRecordCommentPrefix) {
+		return true
+	}
+	if strings.EqualFold(spec.Type, "TXT") {
+		tag := txtTag(spec.Value)
+		return tag != "" && strings.EqualFold(txtTag(existing.Value), tag)
+	}
+	// For single-valued names an identical value means the record is already
+	// what we want, whoever created it.
+	return strings.TrimSpace(spec.Value) == strings.TrimSpace(existing.Value)
+}
+
+// txtTag extracts the leading "v=<protocol>" tag that identifies which mail
+// protocol a TXT record belongs to (RFC 7208 SPF, RFC 6376 DKIM, RFC 7489
+// DMARC, RFC 8461 MTA-STS, RFC 8460 TLS-RPT).
+func txtTag(value string) string {
+	trimmed := strings.TrimSpace(strings.Trim(value, `"`))
+	if !strings.HasPrefix(strings.ToLower(trimmed), "v=") {
+		return ""
+	}
+	rest := trimmed[2:]
+	if idx := strings.IndexAny(rest, "; \t"); idx >= 0 {
+		rest = rest[:idx]
+	}
+	return strings.ToLower(rest)
+}
+
+// allowsCoexistence reports whether several records may share a type and name.
+// TXT is the mail-relevant case: verification tokens from unrelated services
+// live alongside SPF at the zone apex and must not be disturbed.
+func allowsCoexistence(recType string) bool {
+	switch strings.ToUpper(recType) {
+	case "TXT", "MX", "TLSA":
+		return true
+	default:
+		return false
+	}
+}

services/protocols/internal/application/usecase/sync_dns_records_test.go

@@ -9,12 +9,35 @@ import (
 	"lambdamail/protocols/internal/domain/entity"
 )
 
+// fakeDnsProvider models a real zone: several records may share a type and
+// name (multiple TXT at the apex), so records are held in a list keyed by id.
 type fakeDnsProvider struct {
-	records map[string]entity.DnsRecord // key -> record
+	records []entity.DnsRecord
+	nextID  int
 }
 
 func newFakeDnsProvider() *fakeDnsProvider {
-	return &fakeDnsProvider{records: make(map[string]entity.DnsRecord)}
+	return &fakeDnsProvider{}
+}
+
+// seed publishes a pre-existing record that this reconciler did not create.
+func (f *fakeDnsProvider) seed(record entity.DnsRecord) {
+	if record.ID == "" {
+		f.nextID++
+		record.ID = fmt.Sprintf("seed_%d", f.nextID)
+	}
+	f.records = append(f.records, record)
+}
+
+// find returns the records published under a type and name.
+func (f *fakeDnsProvider) find(recType, name string) []entity.DnsRecord {
+	var out []entity.DnsRecord
+	for _, r := range f.records {
+		if strings.EqualFold(r.Type, recType) && strings.EqualFold(r.Name, name) {
+			out = append(out, r)
+		}
+	}
+	return out
 }
 
 func (f *fakeDnsProvider) GetZoneID(_ context.Context, domainName string) (string, error) {
@@ -22,31 +45,31 @@ func (f *fakeDnsProvider) GetZoneID(_ context.Context, domainName string) (strin
 }
 
 func (f *fakeDnsProvider) ListRecords(_ context.Context, _ string) ([]entity.DnsRecord, error) {
-	var out []entity.DnsRecord
-	for _, r := range f.records {
-		out = append(out, r)
-	}
-	return out, nil
+	return append([]entity.DnsRecord(nil), f.records...), nil
 }
 
 func (f *fakeDnsProvider) CreateRecord(_ context.Context, _ string, record entity.DnsRecord) error {
-	key := fmt.Sprintf("%s:%s", strings.ToUpper(record.Type), strings.ToLower(record.Name))
-	record.ID = fmt.Sprintf("id_%s", key)
-	f.records[key] = record
+	f.nextID++
+	record.ID = fmt.Sprintf("id_%d", f.nextID)
+	f.records = append(f.records, record)
 	return nil
 }
 
 func (f *fakeDnsProvider) UpdateRecord(_ context.Context, _ string, record entity.DnsRecord) error {
-	key := fmt.Sprintf("%s:%s", strings.ToUpper(record.Type), strings.ToLower(record.Name))
-	f.records[key] = record
-	return nil
+	for i, r := range f.records {
+		if r.ID == record.ID {
+			f.records[i] = record
+			return nil
+		}
+	}
+	return fmt.Errorf("record %s not found", record.ID)
 }
 
 func (f *fakeDnsProvider) DeleteRecord(_ context.Context, _ string, recordID string) error {
-	for k, r := range f.records {
+	for i, r := range f.records {
 		if r.ID == recordID {
-			delete(f.records, k)
-			break
+			f.records = append(f.records[:i], f.records[i+1:]...)
+			return nil
 		}
 	}
 	return nil
@@ -61,7 +84,11 @@ func (f *fakeSystemAliasRepository) EnsureSystemAliases(_ context.Context, _ str
 	return nil
 }
 
-func TestSyncDnsRecordsUseCase_Creates13RecordsAndAliases(t *testing.T) {
+// The full desired state is the 13 numbered records of PLAN.md section 7.1
+// plus the three client-autoconfiguration records of section 7.2.
+const expectedRecordCount = 16
+
+func TestSyncDnsRecordsUseCase_CreatesFullRecordSetAndAliases(t *testing.T) {
 	dns := newFakeDnsProvider()
 	alias := &fakeSystemAliasRepository{}
 	uc := NewSyncDnsRecordsUseCase(dns, alias)
@@ -85,8 +112,8 @@ func TestSyncDnsRecordsUseCase_Creates13RecordsAndAliases(t *testing.T) {
 		t.Fatalf("Execute failed: %v", err)
 	}
 
-	if out.CreatedCount != 13 {
-		t.Errorf("CreatedCount = %d, want 13", out.CreatedCount)
+	if out.CreatedCount != expectedRecordCount {
+		t.Errorf("CreatedCount = %d, want %d", out.CreatedCount, expectedRecordCount)
 	}
 	if !alias.ensured {
 		t.Error("expected system aliases to be ensured")
@@ -98,7 +125,7 @@ func TestSyncDnsRecordsUseCase_Creates13RecordsAndAliases(t *testing.T) {
 		t.Fatalf("Execute 2 failed: %v", err)
 	}
 
-	if out2.UnchangedCount != 13 || out2.CreatedCount != 0 || out2.UpdatedCount != 0 {
-		t.Errorf("expected 13 unchanged, got created=%d, updated=%d, unchanged=%d", out2.CreatedCount, out2.UpdatedCount, out2.UnchangedCount)
+	if out2.UnchangedCount != expectedRecordCount || out2.CreatedCount != 0 || out2.UpdatedCount != 0 {
+		t.Errorf("expected %d unchanged, got created=%d, updated=%d, unchanged=%d", expectedRecordCount, out2.CreatedCount, out2.UpdatedCount, out2.UnchangedCount)
 	}
 }

services/protocols/internal/domain/entity/dmarc_report.go

@@ -10,12 +10,12 @@ import (
 )
 
 type DmarcRecord struct {
-	SourceIP        string
-	Count           int
-	Disposition     string
-	DKIMResult      string
-	SPFResult       string
-	HeaderFrom      string
+	SourceIP    string
+	Count       int
+	Disposition string
+	DKIMResult  string
+	SPFResult   string
+	HeaderFrom  string
 }
 
 type DmarcReport struct {
@@ -41,8 +41,8 @@ type dmarcXmlReport struct {
 	} `xml:"policy_published"`
 	Record []struct {
 		Row struct {
-			SourceIP string `xml:"source_ip"`
-			Count    int    `xml:"count"`
+			SourceIP        string `xml:"source_ip"`
+			Count           int    `xml:"count"`
 			PolicyEvaluated struct {
 				Disposition string `xml:"disposition"`
 				DKIM        string `xml:"dkim"`

services/protocols/internal/domain/entity/dns_record.go

@@ -1,9 +1,10 @@
 package entity
 
 import (
+	"crypto/sha256"
+	"encoding/binary"
 	"fmt"
 	"strings"
-	"time"
 )
 
 type DnsRecord struct {
@@ -17,8 +18,34 @@ type DnsRecord struct {
 	Comment  string
 }
 
-// Build13DnsRecordSpecs generates the 13 mandatory DNS record specifications per PLAN.md section 7.
-func Build13DnsRecordSpecs(domainName, mailHost, serverIPv4, serverIPv6, rsaDkimPubKey, edDkimPubKey, tlsaHash string, daneEnabled bool) []DnsRecord {
+// DnsRecordSpec describes the zone the reconciler should converge on.
+type DnsRecordSpec struct {
+	DomainName    string
+	MailHost      string
+	ServerIPv4    string
+	ServerIPv6    string
+	RsaDkimPubKey string
+	EdDkimPubKey  string
+	// TlsaHashes are the DANE associations to publish. Two are normally
+	// present during a rollover: the current key and the next one
+	// (RFC 7671 section 8.1).
+	TlsaHashes  []string
+	DaneEnabled bool
+	// RelaySpfInclude is the mechanism authorising a smarthost to send for
+	// this domain. Without it every message the relay forwards fails SPF
+	// (PLAN.md section 10.4).
+	RelaySpfInclude string
+}
+
+// BuildDnsRecordSpecs generates the DNS records of PLAN.md section 7: the 13
+// numbered ones of section 7.1 plus the client-autoconfiguration records of
+// section 7.2.
+func BuildDnsRecordSpecs(spec DnsRecordSpec) []DnsRecord {
+	domainName := spec.DomainName
+	mailHost := spec.MailHost
+	serverIPv4, serverIPv6 := spec.ServerIPv4, spec.ServerIPv6
+	rsaDkimPubKey, edDkimPubKey := spec.RsaDkimPubKey, spec.EdDkimPubKey
+
 	if mailHost == "" {
 		mailHost = fmt.Sprintf("mail.%s", domainName)
 	}
@@ -46,7 +73,7 @@ func Build13DnsRecordSpecs(domainName, mailHost, serverIPv4, serverIPv6, rsaDkim
 		{
 			Type:    "TXT",
 			Name:    domainName,
-			Value:   fmt.Sprintf("v=spf1 mx a:%s -all", mailHost),
+			Value:   buildSpfRecord(mailHost, spec.RelaySpfInclude),
 			TTL:     1,
 			Comment: "LambdaMail SPF Record",
 		},
@@ -78,7 +105,7 @@ func Build13DnsRecordSpecs(domainName, mailHost, serverIPv4, serverIPv6, rsaDkim
 		{
 			Type:    "TXT",
 			Name:    fmt.Sprintf("_mta-sts.%s", domainName),
-			Value:   fmt.Sprintf("v=STSv1; id=%d", time.Now().Unix()),
+			Value:   fmt.Sprintf("v=STSv1; id=%s", mtaStsPolicyID(domainName, mailHost)),
 			TTL:     1,
 			Comment: "LambdaMail MTA-STS Policy Version",
 		},
@@ -117,6 +144,33 @@ func Build13DnsRecordSpecs(domainName, mailHost, serverIPv4, serverIPv6, rsaDkim
 			Priority: intPtr(0),
 			Comment:  "LambdaMail Submissions Autoconfig",
 		},
+		// The remaining client-autoconfiguration records of PLAN.md section
+		// 7.2. They are unnumbered there because they are conveniences, but
+		// the HTTPS endpoints of section 7.3 are unreachable without them.
+		{
+			Type:     "SRV",
+			Name:     fmt.Sprintf("_pop3s._tcp.%s", domainName),
+			Value:    fmt.Sprintf("0 0 995 %s", mailHost),
+			TTL:      1,
+			Priority: intPtr(0),
+			Comment:  "LambdaMail POP3S Autoconfig",
+		},
+		{
+			Type:    "CNAME",
+			Name:    fmt.Sprintf("autoconfig.%s", domainName),
+			Value:   mailHost,
+			TTL:     1,
+			Proxied: true,
+			Comment: "LambdaMail Thunderbird Autoconfig Endpoint",
+		},
+		{
+			Type:     "SRV",
+			Name:     fmt.Sprintf("_autodiscover._tcp.%s", domainName),
+			Value:    fmt.Sprintf("0 0 443 %s", mailHost),
+			TTL:      1,
+			Priority: intPtr(0),
+			Comment:  "LambdaMail Outlook Autodiscover",
+		},
 	}
 
 	// 2. Conditional AAAA record if IPv6 is supplied
@@ -131,24 +185,53 @@ func Build13DnsRecordSpecs(domainName, mailHost, serverIPv4, serverIPv6, rsaDkim
 		})
 	}
 
-	// 11. Conditional TLSA record if DANE is enabled
-	if daneEnabled && tlsaHash != "" {
-		records = append(records, DnsRecord{
-			Type:    "TLSA",
-			Name:    fmt.Sprintf("_25._tcp.%s", mailHost),
-			Value:   fmt.Sprintf("3 1 1 %s", tlsaHash),
-			TTL:     1,
-			Comment: "LambdaMail DANE TLSA Record",
-		})
+	// 11. Conditional TLSA records if DANE is enabled. More than one is normal
+	// during a rollover: the current association and the next one are both
+	// published so the certificate can change without a gap (RFC 7671 8.1).
+	if spec.DaneEnabled {
+		for _, hash := range spec.TlsaHashes {
+			if hash == "" {
+				continue
+			}
+			records = append(records, DnsRecord{
+				Type:    "TLSA",
+				Name:    fmt.Sprintf("_25._tcp.%s", mailHost),
+				Value:   fmt.Sprintf("3 1 1 %s", hash),
+				TTL:     1,
+				Comment: "LambdaMail DANE TLSA Record",
+			})
+		}
 	}
 
 	return records
 }
 
+// buildSpfRecord assembles the sender policy. PLAN.md section 5 uses a hard
+// fail, which is only safe once every legitimate sending path is listed - so
+// the relay, when there is one, has to be included here.
+func buildSpfRecord(mailHost, relayInclude string) string {
+	mechanisms := []string{"v=spf1", "mx", "a:" + mailHost}
+	if relayInclude != "" {
+		mechanisms = append(mechanisms, relayInclude)
+	}
+	return strings.Join(append(mechanisms, "-all"), " ")
+}
+
 func intPtr(v int) *int {
 	return &v
 }
 
+// mtaStsPolicyID derives the MTA-STS policy id from the policy's own content
+// rather than from the wall clock. RFC 8461 section 3.1 requires the id to
+// change whenever the served policy changes; PLAN.md section 7.5 requires the
+// reconciler to be fully idempotent. A timestamp satisfies the first and
+// violates the second - every sync would rewrite the record and force every
+// sender to re-fetch. Hashing the inputs that define the policy satisfies both.
+func mtaStsPolicyID(domainName, mailHost string) string {
+	sum := sha256.Sum256([]byte(domainName + "\x00" + mailHost))
+	return fmt.Sprintf("%016x", binary.BigEndian.Uint64(sum[:8]))
+}
+
 // EqualsNormalized compares two DNS records ignoring subtle formatting whitespace/case differences.
 func (r DnsRecord) EqualsNormalized(other DnsRecord) bool {
 	if r.Type != other.Type {
@@ -163,5 +246,13 @@ func (r DnsRecord) EqualsNormalized(other DnsRecord) bool {
 	if r.Proxied != other.Proxied {
 		return false
 	}
+	// MX and SRV priority drift routes mail to the wrong host, so it counts as
+	// a difference even though the record value itself matches.
+	if (r.Priority == nil) != (other.Priority == nil) {
+		return false
+	}
+	if r.Priority != nil && *r.Priority != *other.Priority {
+		return false
+	}
 	return true
 }

services/protocols/internal/domain/entity/dns_record_test.go

@@ -4,21 +4,43 @@ import (
 	"testing"
 )
 
-func TestBuild13DnsRecordSpecs_GeneratesMandatoryRecords(t *testing.T) {
-	specs := Build13DnsRecordSpecs(
-		"example.test",
-		"mail.example.test",
-		"192.0.2.1",
-		"2001:db8::1",
-		"rsaPubKeyBase64",
-		"edPubKeyBase64",
-		"hash123",
-		true,
-	)
+func TestBuildDnsRecordSpecs_GeneratesMandatoryRecords(t *testing.T) {
+	specs := BuildDnsRecordSpecs(DnsRecordSpec{
+		DomainName:    "example.test",
+		MailHost:      "mail.example.test",
+		ServerIPv4:    "192.0.2.1",
+		ServerIPv6:    "2001:db8::1",
+		RsaDkimPubKey: "rsaPubKeyBase64",
+		EdDkimPubKey:  "edPubKeyBase64",
+		TlsaHashes:    []string{"hash123"},
+		DaneEnabled:   true,
+	})
 
-	// Should contain 13 records (11 mandatory + 1 AAAA + 1 TLSA)
-	if len(specs) != 13 {
-		t.Fatalf("expected 13 records, got %d", len(specs))
+	// PLAN.md section 7.1 numbers 13 records (11 always-on, plus AAAA when
+	// IPv6 is configured and TLSA when DANE is on). Section 7.2 adds three
+	// unnumbered client-autoconfiguration records: the _pop3s SRV, the
+	// autoconfig CNAME and the _autodiscover SRV.
+	const numberedRecords, convenienceRecords = 13, 3
+	if len(specs) != numberedRecords+convenienceRecords {
+		t.Fatalf("expected %d records, got %d", numberedRecords+convenienceRecords, len(specs))
+	}
+
+	// The HTTPS endpoints of section 7.3 are unreachable without the names
+	// that point at them.
+	for _, required := range []struct{ recType, name string }{
+		{"CNAME", "autoconfig.example.test"},
+		{"SRV", "_pop3s._tcp.example.test"},
+		{"SRV", "_autodiscover._tcp.example.test"},
+	} {
+		found := false
+		for _, r := range specs {
+			if r.Type == required.recType && r.Name == required.name {
+				found = true
+			}
+		}
+		if !found {
+			t.Errorf("%s %s not found in specs", required.recType, required.name)
+		}
 	}
 
 	// Verify MX

services/protocols/internal/domain/entity/mailbox.go

@@ -24,7 +24,7 @@ func NewMailbox(domainID uuid.UUID, address valueobject.EmailAddress, hash value
 
 func (m *Mailbox) Address() valueobject.EmailAddress { return m.address }
 func (m *Mailbox) UsedBytes() int64                  { return m.usedBytes }
-func (m *Mailbox) Quota() valueobject.QuotaLimit      { return m.quota }
+func (m *Mailbox) Quota() valueobject.QuotaLimit     { return m.quota }
 
 // RecordUsage sets used_bytes, enforcing "used_bytes <= quota_bytes" (PLAN.md section 3).
 func (m *Mailbox) RecordUsage(bytes int64) error {

services/protocols/internal/domain/entity/outbound_job.go

@@ -36,15 +36,23 @@ type OutboundJob struct {
 	CreatedAt         time.Time
 }
 
-// CalculateNextBackoff computes the next retry time and DSN requirements based on attempt count.
-func CalculateNextBackoff(now time.Time, attempt int, expiresAt time.Time) (nextAttemptAt time.Time, sendDelayDsn bool, permanentFailure bool) {
+// CalculateNextBackoff computes the next retry time and DSN requirements from
+// the attempt that has just failed. The delays follow PLAN.md section 6.3,
+// which tabulates the wait *before* each attempt: attempt 2 runs 5 min after
+// attempt 1 failed, attempt 4 an hour later and also emits the delay DSN, and
+// from attempt 5 on the wait carries +/-20% jitter to avoid a thundering herd.
+func CalculateNextBackoff(now time.Time, failedAttempt int, expiresAt time.Time) (nextAttemptAt time.Time, sendDelayDsn bool, permanentFailure bool) {
 	if !expiresAt.IsZero() && (now.After(expiresAt) || now.Equal(expiresAt)) {
 		return now, false, true
 	}
 
+	// The delay to apply is the one the retry table associates with the
+	// attempt about to be scheduled, not with the one that just failed.
+	nextAttempt := failedAttempt + 1
+
 	var baseDelay time.Duration
 
-	switch attempt {
+	switch nextAttempt {
 	case 1:
 		baseDelay = 0
 	case 2:
@@ -64,8 +72,8 @@ func CalculateNextBackoff(now time.Time, attempt int, expiresAt time.Time) (next
 		baseDelay = 12 * time.Hour
 	}
 
-	if baseDelay > 0 && attempt >= 5 {
-		// Apply ±20% jitter
+	if baseDelay > 0 && nextAttempt >= 5 {
+		// Apply +/-20% jitter
 		jitterFactor := 0.8 + rand.Float64()*0.4
 		baseDelay = time.Duration(float64(baseDelay) * jitterFactor)
 	}

services/protocols/internal/domain/entity/outbound_job_test.go

@@ -5,26 +5,50 @@ import (
 	"time"
 )
 
-func TestCalculateNextBackoff_SchedulesCorrectDelays(t *testing.T) {
+// PLAN.md section 6.3 defines the wait *before the next* attempt: after
+// attempt 1 fails the next try is +5 min, after attempt 3 it is +1 h together
+// with the delay DSN, and from the fifth try on the delay carries +/-20%
+// jitter. A zero delay after the first failure would hammer the destination in
+// a tight loop.
+func TestCalculateNextBackoff_FollowsRetryTable(t *testing.T) {
 	now := time.Now()
 	expiresAt := now.Add(5 * 24 * time.Hour)
 
-	// Attempt 2 -> +5 min
-	next, delayDsn, perm := CalculateNextBackoff(now, 2, expiresAt)
-	if perm || delayDsn || next.Sub(now) < 4*time.Minute {
-		t.Errorf("attempt 2 backoff mismatch: next=%v, delayDsn=%v, perm=%v", next, delayDsn, perm)
+	cases := []struct {
+		failedAttempt int
+		wantMin       time.Duration
+		wantMax       time.Duration
+		wantDelayDsn  bool
+	}{
+		{1, 5 * time.Minute, 5 * time.Minute, false},
+		{2, 15 * time.Minute, 15 * time.Minute, false},
+		{3, time.Hour, time.Hour, true},
+		{4, 96 * time.Minute, 144 * time.Minute, false},   // 2 h +/- 20%
+		{5, 192 * time.Minute, 288 * time.Minute, false},  // 4 h +/- 20%
+		{6, 384 * time.Minute, 576 * time.Minute, false},  // 8 h +/- 20%
+		{7, 576 * time.Minute, 864 * time.Minute, false},  // 12 h +/- 20%
+		{20, 576 * time.Minute, 864 * time.Minute, false}, // steady 12 h
 	}
 
-	// Attempt 4 -> +1 hr + delayDsn=true
-	next, delayDsn, perm = CalculateNextBackoff(now, 4, expiresAt)
-	if perm || !delayDsn || next.Sub(now) < 55*time.Minute {
-		t.Errorf("attempt 4 backoff mismatch: next=%v, delayDsn=%v, perm=%v", next, delayDsn, perm)
+	for _, tc := range cases {
+		next, delayDsn, perm := CalculateNextBackoff(now, tc.failedAttempt, expiresAt)
+		if perm {
+			t.Errorf("attempt %d: unexpected permanent failure", tc.failedAttempt)
+			continue
+		}
+		got := next.Sub(now)
+		if got < tc.wantMin || got > tc.wantMax {
+			t.Errorf("attempt %d: delay = %v, want between %v and %v", tc.failedAttempt, got, tc.wantMin, tc.wantMax)
+		}
+		if delayDsn != tc.wantDelayDsn {
+			t.Errorf("attempt %d: delayDsn = %v, want %v", tc.failedAttempt, delayDsn, tc.wantDelayDsn)
+		}
 	}
+}
 
-	// Expired -> permanent failure
-	expiredTime := now.Add(-1 * time.Hour)
-	_, _, perm = CalculateNextBackoff(now, 5, expiredTime)
-	if !perm {
-		t.Errorf("expected permanent failure for expired job")
+func TestCalculateNextBackoff_ExpiredJobIsPermanent(t *testing.T) {
+	now := time.Now()
+	if _, _, perm := CalculateNextBackoff(now, 5, now.Add(-time.Hour)); !perm {
+		t.Error("expected permanent failure for an expired job")
 	}
 }

services/protocols/internal/domain/entity/sieve_validator.go

@@ -7,10 +7,10 @@ import (
 )
 
 var (
-	ErrEmptyScript       = errors.New("sieve script cannot be empty")
-	ErrUnmatchedBrace    = errors.New("unmatched curly brace in sieve script")
-	ErrUnmatchedBracket  = errors.New("unmatched square bracket in sieve script")
-	ErrUnterminatedQuote = errors.New("unterminated string literal in sieve script")
+	ErrEmptyScript         = errors.New("sieve script cannot be empty")
+	ErrUnmatchedBrace      = errors.New("unmatched curly brace in sieve script")
+	ErrUnmatchedBracket    = errors.New("unmatched square bracket in sieve script")
+	ErrUnterminatedQuote   = errors.New("unterminated string literal in sieve script")
 	ErrUnterminatedComment = errors.New("unterminated comment block in sieve script")
 )
 

services/protocols/internal/domain/entity/sieve_validator_test.go

@@ -32,8 +32,8 @@ if size :over 1M {
 
 func TestValidateSieveScript_InvalidScripts(t *testing.T) {
 	tests := []struct {
-		name   string
-		script string
+		name    string
+		script  string
 		wantErr error
 	}{
 		{"empty", "", ErrEmptyScript},

services/protocols/internal/domain/entity/tls_policy.go

@@ -1,25 +1,155 @@
 package entity
 
-// TLSPolicy is the effective transport security policy for an outbound destination
-// (PLAN.md section 3: DANE has precedence over MTA-STS, RFC 8461 section 2).
+import (
+	"crypto/sha256"
+	"crypto/x509"
+	"encoding/hex"
+	"strings"
+
+	"lambdamail/protocols/internal/domain/valueobject"
+)
+
+// Transport security modes, in the precedence order of RFC 8461 section 2:
+// DANE wins when TLSA records exist, MTA-STS applies otherwise, and a
+// destination with neither gets opportunistic TLS (RFC 7435).
+const (
+	TLSModeDane          = "dane"
+	TLSModeMtaSts        = "mta-sts"
+	TLSModeOpportunistic = "opportunistic"
+	// TLSModeRelay records that the message left through a smarthost, which
+	// owns transport security from that point on (PLAN.md section 10.4).
+	TLSModeRelay = "relay"
+)
+
+// TLSPolicy is the effective transport security policy for one outbound
+// destination (PLAN.md sections 5 and 6.2).
 type TLSPolicy struct {
 	daneAvailable   bool
 	mtaSTSAvailable bool
+
+	// enforce is true when a validation failure must defer the message
+	// instead of falling back to an unvalidated connection. It is false for
+	// MTA-STS "testing", whose whole purpose is to report without breaking.
+	enforce bool
+
+	// mxPatterns are the "mx:" entries of the MTA-STS policy. A host that
+	// matches none of them is not covered by the policy.
+	mxPatterns []string
+
+	// tlsaRecords are the DANE-EE associations published for the target host.
+	tlsaRecords []valueobject.TLSARecord
 }
 
+// NewTLSPolicy builds an opportunistic-or-simple policy. It is kept for
+// callers that only need the precedence decision.
 func NewTLSPolicy(daneAvailable, mtaSTSAvailable bool) TLSPolicy {
 	return TLSPolicy{daneAvailable: daneAvailable, mtaSTSAvailable: mtaSTSAvailable}
 }
 
-// Effective returns "dane", "mta-sts" or "opportunistic" following the precedence
-// rule in PLAN.md section 5 / RFC 8461 section 2.
+// NewDanePolicy builds a policy backed by TLSA records. DANE is always
+// enforcing: the records are DNSSEC-signed, so a mismatch is an attack or a
+// misconfiguration, never an acceptable downgrade (RFC 7672 section 2.2).
+func NewDanePolicy(records []valueobject.TLSARecord) TLSPolicy {
+	return TLSPolicy{daneAvailable: true, enforce: true, tlsaRecords: records}
+}
+
+// NewMtaStsPolicy builds a policy from a fetched MTA-STS policy file.
+func NewMtaStsPolicy(mxPatterns []string, enforce bool) TLSPolicy {
+	return TLSPolicy{mtaSTSAvailable: true, enforce: enforce, mxPatterns: mxPatterns}
+}
+
+// Effective returns "dane", "mta-sts" or "opportunistic" following the
+// precedence rule in PLAN.md section 5 / RFC 8461 section 2.
 func (p TLSPolicy) Effective() string {
 	switch {
 	case p.daneAvailable:
-		return "dane"
+		return TLSModeDane
 	case p.mtaSTSAvailable:
-		return "mta-sts"
+		return TLSModeMtaSts
 	default:
-		return "opportunistic"
+		return TLSModeOpportunistic
+	}
+}
+
+// RequiresValidation reports whether the connection's certificate has to be
+// checked before any mail is handed over.
+func (p TLSPolicy) RequiresValidation() bool {
+	return p.enforce && (p.daneAvailable || p.mtaSTSAvailable)
+}
+
+// CoversHost reports whether a candidate MX is inside the policy's scope. An
+// MTA-STS policy that does not list the host means the host must not be used
+// under that policy (RFC 8461 section 4.1).
+func (p TLSPolicy) CoversHost(host string) bool {
+	if !p.mtaSTSAvailable {
+		return true
+	}
+	for _, pattern := range p.mxPatterns {
+		if matchMxPattern(pattern, host) {
+			return true
+		}
+	}
+	return false
+}
+
+// matchMxPattern implements the single-label wildcard of RFC 8461 section 4.1:
+// "*.example.com" matches "mx1.example.com" but not "a.mx1.example.com".
+func matchMxPattern(pattern, host string) bool {
+	pattern = strings.ToLower(strings.TrimSuffix(pattern, "."))
+	host = strings.ToLower(strings.TrimSuffix(host, "."))
+
+	if !strings.HasPrefix(pattern, "*.") {
+		return pattern == host
+	}
+
+	suffix := pattern[1:] // ".example.com"
+	if !strings.HasSuffix(host, suffix) {
+		return false
+	}
+	label := strings.TrimSuffix(host, suffix)
+	return label != "" && !strings.Contains(label, ".")
+}
+
+// MatchesCertificate checks a presented certificate chain against the DANE
+// associations. Only usage 3 (DANE-EE) is supported by explicit decision
+// (PLAN.md section 5.1), so the end-entity certificate is what gets matched
+// and the PKIX chain is irrelevant.
+func (p TLSPolicy) MatchesCertificate(chain []*x509.Certificate) bool {
+	if len(p.tlsaRecords) == 0 || len(chain) == 0 {
+		return false
+	}
+
+	leaf := chain[0]
+	for _, record := range p.tlsaRecords {
+		if digestFor(leaf, record) == strings.ToLower(record.Data()) {
+			return true
+		}
+	}
+	return false
+}
+
+// digestFor renders the certificate the way a TLSA record's selector and
+// matching type describe it (RFC 6698 section 2.1.2).
+func digestFor(cert *x509.Certificate, record valueobject.TLSARecord) string {
+	var material []byte
+	switch record.Selector() {
+	case 0: // full certificate
+		material = cert.Raw
+	case 1: // SubjectPublicKeyInfo
+		material = cert.RawSubjectPublicKeyInfo
+	default:
+		return ""
+	}
+
+	switch record.MatchingType() {
+	case 0: // exact match on the material itself
+		return strings.ToLower(hex.EncodeToString(material))
+	case 1: // SHA-256
+		sum := sha256.Sum256(material)
+		return hex.EncodeToString(sum[:])
+	default:
+		// SHA-512 (type 2) is deliberately unsupported: the reconciler only
+		// ever publishes "3 1 1" records (PLAN.md section 7.1).
+		return ""
 	}
 }

services/protocols/internal/domain/event/events.go

@@ -13,75 +13,75 @@ type DomainEvent interface {
 
 type EmailReceived struct{ MessageAggregateID uuid.UUID }
 
-func (e EmailReceived) Type() string          { return "EmailReceived" }
+func (e EmailReceived) Type() string           { return "EmailReceived" }
 func (e EmailReceived) AggregateID() uuid.UUID { return e.MessageAggregateID }
 
 type EmailAccepted struct{ MessageAggregateID uuid.UUID }
 
-func (e EmailAccepted) Type() string          { return "EmailAccepted" }
+func (e EmailAccepted) Type() string           { return "EmailAccepted" }
 func (e EmailAccepted) AggregateID() uuid.UUID { return e.MessageAggregateID }
 
 type EmailDelivered struct{ JobAggregateID uuid.UUID }
 
-func (e EmailDelivered) Type() string          { return "EmailDelivered" }
+func (e EmailDelivered) Type() string           { return "EmailDelivered" }
 func (e EmailDelivered) AggregateID() uuid.UUID { return e.JobAggregateID }
 
 type EmailDeferred struct{ JobAggregateID uuid.UUID }
 
-func (e EmailDeferred) Type() string          { return "EmailDeferred" }
+func (e EmailDeferred) Type() string           { return "EmailDeferred" }
 func (e EmailDeferred) AggregateID() uuid.UUID { return e.JobAggregateID }
 
 type EmailBounced struct{ JobAggregateID uuid.UUID }
 
-func (e EmailBounced) Type() string          { return "EmailBounced" }
+func (e EmailBounced) Type() string           { return "EmailBounced" }
 func (e EmailBounced) AggregateID() uuid.UUID { return e.JobAggregateID }
 
 type MailboxQuotaWarning struct{ MailboxAggregateID uuid.UUID }
 
-func (e MailboxQuotaWarning) Type() string          { return "MailboxQuotaWarning" }
+func (e MailboxQuotaWarning) Type() string           { return "MailboxQuotaWarning" }
 func (e MailboxQuotaWarning) AggregateID() uuid.UUID { return e.MailboxAggregateID }
 
 type MailboxQuotaExceeded struct{ MailboxAggregateID uuid.UUID }
 
-func (e MailboxQuotaExceeded) Type() string          { return "MailboxQuotaExceeded" }
+func (e MailboxQuotaExceeded) Type() string           { return "MailboxQuotaExceeded" }
 func (e MailboxQuotaExceeded) AggregateID() uuid.UUID { return e.MailboxAggregateID }
 
 type SpamDetected struct{ MessageAggregateID uuid.UUID }
 
-func (e SpamDetected) Type() string          { return "SpamDetected" }
+func (e SpamDetected) Type() string           { return "SpamDetected" }
 func (e SpamDetected) AggregateID() uuid.UUID { return e.MessageAggregateID }
 
 type VirusDetected struct{ MessageAggregateID uuid.UUID }
 
-func (e VirusDetected) Type() string          { return "VirusDetected" }
+func (e VirusDetected) Type() string           { return "VirusDetected" }
 func (e VirusDetected) AggregateID() uuid.UUID { return e.MessageAggregateID }
 
 type DkimRotationStarted struct{ DomainAggregateID uuid.UUID }
 
-func (e DkimRotationStarted) Type() string          { return "DkimRotationStarted" }
+func (e DkimRotationStarted) Type() string           { return "DkimRotationStarted" }
 func (e DkimRotationStarted) AggregateID() uuid.UUID { return e.DomainAggregateID }
 
 type DkimRotationCompleted struct{ DomainAggregateID uuid.UUID }
 
-func (e DkimRotationCompleted) Type() string          { return "DkimRotationCompleted" }
+func (e DkimRotationCompleted) Type() string           { return "DkimRotationCompleted" }
 func (e DkimRotationCompleted) AggregateID() uuid.UUID { return e.DomainAggregateID }
 
 type DnsRecordDrifted struct{ DomainAggregateID uuid.UUID }
 
-func (e DnsRecordDrifted) Type() string          { return "DnsRecordDrifted" }
+func (e DnsRecordDrifted) Type() string           { return "DnsRecordDrifted" }
 func (e DnsRecordDrifted) AggregateID() uuid.UUID { return e.DomainAggregateID }
 
 type CertificateRotated struct{ HostAggregateID uuid.UUID }
 
-func (e CertificateRotated) Type() string          { return "CertificateRotated" }
+func (e CertificateRotated) Type() string           { return "CertificateRotated" }
 func (e CertificateRotated) AggregateID() uuid.UUID { return e.HostAggregateID }
 
 type AuthenticationFailed struct{ MailboxAggregateID uuid.UUID }
 
-func (e AuthenticationFailed) Type() string          { return "AuthenticationFailed" }
+func (e AuthenticationFailed) Type() string           { return "AuthenticationFailed" }
 func (e AuthenticationFailed) AggregateID() uuid.UUID { return e.MailboxAggregateID }
 
 type RateLimitTriggered struct{ SubjectAggregateID uuid.UUID }
 
-func (e RateLimitTriggered) Type() string          { return "RateLimitTriggered" }
+func (e RateLimitTriggered) Type() string           { return "RateLimitTriggered" }
 func (e RateLimitTriggered) AggregateID() uuid.UUID { return e.SubjectAggregateID }

services/protocols/internal/domain/valueobject/domain_name.go

@@ -11,9 +11,9 @@ type DomainName struct {
 }
 
 var (
-	ErrDomainNameEmpty         = errors.New("domain name: must not be empty")
-	ErrDomainNameNotFQDN       = errors.New("domain name: must contain at least one dot (not a FQDN)")
-	ErrDomainNameInvalidLabel  = errors.New("domain name: label must not start or end with a hyphen")
+	ErrDomainNameEmpty        = errors.New("domain name: must not be empty")
+	ErrDomainNameNotFQDN      = errors.New("domain name: must contain at least one dot (not a FQDN)")
+	ErrDomainNameInvalidLabel = errors.New("domain name: label must not start or end with a hyphen")
 )
 
 // NewDomainName validates and normalizes raw into a DomainName.

services/protocols/internal/domain/valueobject/email_address.go

@@ -14,9 +14,9 @@ type EmailAddress struct {
 }
 
 var (
-	ErrEmailMissingAtSign  = errors.New("email address: missing '@' separator")
-	ErrEmailEmptyLocalPart = errors.New("email address: local part must not be empty")
-	ErrEmailEmptyDomain    = errors.New("email address: domain must not be empty")
+	ErrEmailMissingAtSign    = errors.New("email address: missing '@' separator")
+	ErrEmailEmptyLocalPart   = errors.New("email address: local part must not be empty")
+	ErrEmailEmptyDomain      = errors.New("email address: domain must not be empty")
 	ErrEmailLocalPartTooLong = errors.New("email address: local part exceeds 64 octets (RFC 5321 4.5.3.1.1)")
 )
 

services/protocols/internal/domain/valueobject/message_id.go

@@ -11,7 +11,7 @@ type MessageID struct {
 }
 
 var (
-	ErrMessageIDEmpty       = errors.New("message id: must not be empty")
+	ErrMessageIDEmpty        = errors.New("message id: must not be empty")
 	ErrMessageIDNotBracketed = errors.New("message id: must be wrapped in angle brackets")
 )
 

services/protocols/internal/domain/valueobject/spam_verdict_test.go

@@ -12,7 +12,7 @@ func TestSpamVerdictFromScore_MatchesThresholds(t *testing.T) {
 		{3.9, SpamHam},
 		{4, SpamProbable},
 		{8.9, SpamProbable},
-		{9, SpamReject},   // section 10.1: 9-15 greylists/defers, modeled here as reject-eligible
+		{9, SpamReject}, // section 10.1: 9-15 greylists/defers, modeled here as reject-eligible
 		{15.1, SpamReject},
 	}
 	for _, c := range cases {

services/protocols/internal/e2e/antispam_antivirus_e2e_test.go

@@ -6,14 +6,12 @@ import (
 	"net"
 	"net/http"
 	"net/http/httptest"
-	"os"
-	"path/filepath"
 	"strings"
 	"testing"
 	"time"
 
-	embeddedpostgres "github.com/fergusstrange/embedded-postgres"
 	gosmtp "github.com/emersion/go-smtp"
+	embeddedpostgres "github.com/fergusstrange/embedded-postgres"
 	"github.com/google/uuid"
 
 	appusecase "lambdamail/protocols/internal/application/usecase"
@@ -47,22 +45,7 @@ func TestAntispamAntivirusEndToEnd(t *testing.T) {
 	}
 	defer pool.Close()
 
-	root := repoRoot(t)
-	migrations := []string{
-		"0001_init_schema.up.sql",
-		"0002_add_is_system_to_aliases.up.sql",
-		"0003_create_report_tables.up.sql",
-	}
-
-	for _, m := range migrations {
-		sql, err := os.ReadFile(filepath.Join(root, "migrations", m))
-		if err != nil {
-			t.Fatalf("read migration %s: %v", m, err)
-		}
-		if _, err := pool.Exec(ctx, string(sql)); err != nil {
-			t.Fatalf("apply migration %s: %v", m, err)
-		}
-	}
+	applyMigrations(t, ctx, pool)
 
 	// Seed domain, mailbox, INBOX and Junk folders
 	domainID := uuid.New()

services/protocols/internal/e2e/dns_sync_e2e_test.go

@@ -2,13 +2,11 @@ package e2e
 
 import (
 	"context"
-	"os"
-	"path/filepath"
 	"testing"
 	"time"
 
-	"github.com/google/uuid"
 	embeddedpostgres "github.com/fergusstrange/embedded-postgres"
+	"github.com/google/uuid"
 
 	appusecase "lambdamail/protocols/internal/application/usecase"
 	"lambdamail/protocols/internal/domain/entity"
@@ -38,21 +36,7 @@ func TestDnsSyncAndSystemAliasesEndToEnd(t *testing.T) {
 	}
 	defer pool.Close()
 
-	root := repoRoot(t)
-	migrations := []string{
-		"0001_init_schema.up.sql",
-		"0002_add_is_system_to_aliases.up.sql",
-		"0003_create_report_tables.up.sql",
-	}
-	for _, m := range migrations {
-		sql, err := os.ReadFile(filepath.Join(root, "migrations", m))
-		if err != nil {
-			t.Fatalf("read migration %s: %v", m, err)
-		}
-		if _, err := pool.Exec(ctx, string(sql)); err != nil {
-			t.Fatalf("apply migration %s: %v", m, err)
-		}
-	}
+	applyMigrations(t, ctx, pool)
 
 	// Seed domain & admin mailbox
 	domainID := uuid.New()
@@ -86,8 +70,11 @@ func TestDnsSyncAndSystemAliasesEndToEnd(t *testing.T) {
 		t.Fatalf("SyncDnsRecords execute: %v", err)
 	}
 
-	if out.CreatedCount != 13 {
-		t.Errorf("CreatedCount = %d, want 13", out.CreatedCount)
+	// The 13 numbered records of PLAN.md section 7.1 plus the three
+	// client-autoconfiguration records of section 7.2.
+	const expectedRecords = 16
+	if out.CreatedCount != expectedRecords {
+		t.Errorf("CreatedCount = %d, want %d", out.CreatedCount, expectedRecords)
 	}
 
 	// Verify 4 system aliases in PostgreSQL (postmaster@, abuse@, dmarc@, tlsrpt@)

services/protocols/internal/e2e/f2_complete_e2e_test.go

@@ -7,8 +7,6 @@ import (
 	"encoding/base64"
 	"fmt"
 	"net"
-	"os"
-	"path/filepath"
 	"strings"
 	"testing"
 	"time"
@@ -52,21 +50,7 @@ func TestF2CompleteSuiteEndToEnd(t *testing.T) {
 	}
 	defer pool.Close()
 
-	root := repoRoot(t)
-	migrations := []string{
-		"0001_init_schema.up.sql",
-		"0002_add_is_system_to_aliases.up.sql",
-		"0003_create_report_tables.up.sql",
-	}
-	for _, m := range migrations {
-		sql, err := os.ReadFile(filepath.Join(root, "migrations", m))
-		if err != nil {
-			t.Fatalf("read migration %s: %v", m, err)
-		}
-		if _, err := pool.Exec(ctx, string(sql)); err != nil {
-			t.Fatalf("apply migration %s: %v", m, err)
-		}
-	}
+	applyMigrations(t, ctx, pool)
 
 	// 2. Seed domain, mailbox, INBOX, Archive
 	password := "correct horse battery staple"
@@ -443,7 +427,7 @@ func TestF2CompleteSuiteEndToEnd(t *testing.T) {
 		t.Fatalf("SETACTIVE = %q", activeResp)
 	}
 
-	// Verify RFC 5804 §2.7: DELETESCRIPT on active script MUST fail
+	// Verify RFC 5804 section 2.7: DELETESCRIPT on active script MUST fail
 	sendCmdSieve("DELETESCRIPT \"auto_rules\"")
 	if delActiveResp := readLineSieve(); !strings.HasPrefix(delActiveResp, "NO") {
 		t.Fatalf("expected NO for deleting active script, got %q", delActiveResp)

services/protocols/internal/e2e/f3_complete_e2e_test.go

@@ -8,8 +8,6 @@ import (
 	"net"
 	"net/http"
 	"net/http/httptest"
-	"os"
-	"path/filepath"
 	"strings"
 	"testing"
 	"time"
@@ -19,12 +17,14 @@ import (
 
 	appusecase "lambdamail/protocols/internal/application/usecase"
 	"lambdamail/protocols/internal/domain/entity"
+	"lambdamail/protocols/internal/domain/valueobject"
 	"lambdamail/protocols/internal/infrastructure/clamav"
 	"lambdamail/protocols/internal/infrastructure/diskstorage"
 	"lambdamail/protocols/internal/infrastructure/postgres"
 	"lambdamail/protocols/internal/infrastructure/rspamd"
 	httppresentation "lambdamail/protocols/internal/presentation/http"
 	smtppresentation "lambdamail/protocols/internal/presentation/smtp"
+
 	gosmtp "github.com/emersion/go-smtp"
 )
 
@@ -96,22 +96,7 @@ func TestPhase3CompleteEndToEnd(t *testing.T) {
 	defer pool.Close()
 
 	// Apply Database Migrations
-	root := repoRoot(t)
-	migrations := []string{
-		"0001_init_schema.up.sql",
-		"0002_add_is_system_to_aliases.up.sql",
-		"0003_create_report_tables.up.sql",
-	}
-
-	for _, m := range migrations {
-		sql, err := os.ReadFile(filepath.Join(root, "migrations", m))
-		if err != nil {
-			t.Fatalf("read migration %s: %v", m, err)
-		}
-		if _, err := pool.Exec(ctx, string(sql)); err != nil {
-			t.Fatalf("apply migration %s: %v", m, err)
-		}
-	}
+	applyMigrations(t, ctx, pool)
 
 	// -------------------------------------------------------------------
 	// 1. Sub-project 1: Cloudflare DNS Automation Engine & System Aliases
@@ -156,8 +141,14 @@ func TestPhase3CompleteEndToEnd(t *testing.T) {
 	if err != nil {
 		t.Fatalf("sync dns records: %v", err)
 	}
-	if dnsOut.CreatedCount != 13 {
-		t.Fatalf("expected 13 created DNS records, got %d", dnsOut.CreatedCount)
+	// The 13 numbered records of PLAN.md section 7.1 plus the three
+	// client-autoconfiguration records of section 7.2.
+	const expectedDnsRecords = 16
+	if dnsOut.CreatedCount != expectedDnsRecords {
+		t.Fatalf("expected %d created DNS records, got %d", expectedDnsRecords, dnsOut.CreatedCount)
+	}
+	if dnsOut.Status != appusecase.SyncStatusVerified {
+		t.Errorf("sync status = %s, want VERIFIED", dnsOut.Status)
 	}
 
 	// Verify system aliases created
@@ -174,14 +165,26 @@ func TestPhase3CompleteEndToEnd(t *testing.T) {
 	reportUC := appusecase.NewIngestReportsUseCase(reportRepo)
 	httpRouter := httppresentation.NewRouter(reportUC, func() error { return pool.Ping(ctx) })
 
-	// Test MTA-STS endpoint
+	// Test MTA-STS endpoint. The default is the safe end of the ramp
+	// (PLAN.md section 5): senders honour the policy but do not hard-fail on
+	// it until the operator promotes the domain to enforce.
 	reqSts := httptest.NewRequest("GET", "/.well-known/mta-sts.txt", nil)
 	reqSts.Host = "mta-sts.f3e2e.test"
 	recSts := httptest.NewRecorder()
 	httpRouter.ServeHTTP(recSts, reqSts)
-	if recSts.Code != http.StatusOK || !strings.Contains(recSts.Body.String(), "mode: enforce") {
+	if recSts.Code != http.StatusOK || !strings.Contains(recSts.Body.String(), "mode: testing") {
 		t.Errorf("MTA-STS endpoint error: code=%d body=%s", recSts.Code, recSts.Body.String())
 	}
+	if !strings.Contains(recSts.Body.String(), "mx: mail.f3e2e.test") {
+		t.Errorf("MTA-STS policy does not advertise the mail host: %s", recSts.Body.String())
+	}
+
+	httpRouter.SetMtaStsMode(valueobject.MtaStsModeEnforce)
+	recEnforced := httptest.NewRecorder()
+	httpRouter.ServeHTTP(recEnforced, httptest.NewRequest("GET", "/.well-known/mta-sts.txt", nil))
+	if !strings.Contains(recEnforced.Body.String(), "mode: enforce") {
+		t.Errorf("promoting the domain to enforce had no effect: %s", recEnforced.Body.String())
+	}
 
 	// Test Autoconfig endpoint
 	reqAuto := httptest.NewRequest("GET", "/.well-known/autoconfig/mail/config-v1.1.xml", nil)

services/protocols/internal/e2e/http_services_e2e_test.go

@@ -6,8 +6,6 @@ import (
 	"io"
 	"net/http"
 	"net/http/httptest"
-	"os"
-	"path/filepath"
 	"strings"
 	"testing"
 	"time"
@@ -42,22 +40,7 @@ func TestHttpServicesEndToEnd(t *testing.T) {
 	}
 	defer pool.Close()
 
-	root := repoRoot(t)
-	migrations := []string{
-		"0001_init_schema.up.sql",
-		"0002_add_is_system_to_aliases.up.sql",
-		"0003_create_report_tables.up.sql",
-	}
-
-	for _, m := range migrations {
-		sql, err := os.ReadFile(filepath.Join(root, "migrations", m))
-		if err != nil {
-			t.Fatalf("read migration %s: %v", m, err)
-		}
-		if _, err := pool.Exec(ctx, string(sql)); err != nil {
-			t.Fatalf("apply migration %s: %v", m, err)
-		}
-	}
+	applyMigrations(t, ctx, pool)
 
 	reportRepo := postgres.NewReportRepository(pool)
 	reportUseCase := appusecase.NewIngestReportsUseCase(reportRepo)

services/protocols/internal/e2e/imap_core_e2e_test.go

@@ -10,13 +10,13 @@ import (
 	"time"
 
 	"github.com/alexedwards/argon2id"
-	embeddedpostgres "github.com/fergusstrange/embedded-postgres"
 	"github.com/emersion/go-imap/v2"
 	"github.com/emersion/go-imap/v2/imapclient"
 	"github.com/emersion/go-imap/v2/imapserver"
+	embeddedpostgres "github.com/fergusstrange/embedded-postgres"
 
-	appusecase "lambdamail/protocols/internal/application/usecase"
 	"lambdamail/protocols/internal/application/port"
+	appusecase "lambdamail/protocols/internal/application/usecase"
 	"lambdamail/protocols/internal/infrastructure/diskstorage"
 	"lambdamail/protocols/internal/infrastructure/postgres"
 	imappresentation "lambdamail/protocols/internal/presentation/imap"

services/protocols/internal/e2e/imap_idle_condstore_e2e_test.go

@@ -10,13 +10,13 @@ import (
 	"time"
 
 	"github.com/alexedwards/argon2id"
-	embeddedpostgres "github.com/fergusstrange/embedded-postgres"
 	"github.com/emersion/go-imap/v2"
 	"github.com/emersion/go-imap/v2/imapclient"
 	"github.com/emersion/go-imap/v2/imapserver"
+	embeddedpostgres "github.com/fergusstrange/embedded-postgres"
 
-	appusecase "lambdamail/protocols/internal/application/usecase"
 	"lambdamail/protocols/internal/application/port"
+	appusecase "lambdamail/protocols/internal/application/usecase"
 	"lambdamail/protocols/internal/infrastructure/diskstorage"
 	"lambdamail/protocols/internal/infrastructure/postgres"
 	imappresentation "lambdamail/protocols/internal/presentation/imap"

services/protocols/internal/e2e/migrations_test.go

@@ -0,0 +1,79 @@
+package e2e
+
+import (
+	"context"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/tls"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"math/big"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+// applyMigrations brings a fresh database up to the current schema by running
+// every up-migration in order. It reads the directory instead of taking a
+// hand-written list so that adding a migration cannot leave a test silently
+// running against a stale schema.
+func applyMigrations(t *testing.T, ctx context.Context, pool *pgxpool.Pool) {
+	t.Helper()
+
+	dir := filepath.Join(repoRoot(t), "migrations")
+	entries, err := os.ReadDir(dir)
+	if err != nil {
+		t.Fatalf("read migrations dir: %v", err)
+	}
+
+	var names []string
+	for _, e := range entries {
+		if !e.IsDir() && strings.HasSuffix(e.Name(), ".up.sql") {
+			names = append(names, e.Name())
+		}
+	}
+	if len(names) == 0 {
+		t.Fatalf("no up-migrations found in %s", dir)
+	}
+	sort.Strings(names)
+
+	for _, name := range names {
+		sql, err := os.ReadFile(filepath.Join(dir, name))
+		if err != nil {
+			t.Fatalf("read migration %s: %v", name, err)
+		}
+		if _, err := pool.Exec(ctx, string(sql)); err != nil {
+			t.Fatalf("apply migration %s: %v", name, err)
+		}
+	}
+}
+
+// selfSignedTLSCert issues an in-memory certificate for the STARTTLS handshake
+// in tests. Certificate validation is not what these tests exercise.
+func selfSignedTLSCert(t *testing.T) tls.Certificate {
+	t.Helper()
+
+	key, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	if err != nil {
+		t.Fatalf("generate key: %v", err)
+	}
+	template := &x509.Certificate{
+		SerialNumber: big.NewInt(1),
+		Subject:      pkix.Name{CommonName: "mail.test"},
+		DNSNames:     []string{"mail.test", "localhost"},
+		NotBefore:    time.Now().Add(-time.Hour),
+		NotAfter:     time.Now().Add(24 * time.Hour),
+	}
+	der, err := x509.CreateCertificate(rand.Reader, template, template, &key.PublicKey, key)
+	if err != nil {
+		t.Fatalf("create certificate: %v", err)
+	}
+
+	return tls.Certificate{Certificate: [][]byte{der}, PrivateKey: key}
+}

services/protocols/internal/e2e/outbound_queue_e2e_test.go

@@ -4,8 +4,6 @@ import (
 	"bufio"
 	"context"
 	"net"
-	"os"
-	"path/filepath"
 	"strings"
 	"testing"
 	"time"
@@ -50,22 +48,7 @@ func TestOutboundQueueEndToEnd(t *testing.T) {
 	}
 	defer pool.Close()
 
-	root := repoRoot(t)
-	migrations := []string{
-		"0001_init_schema.up.sql",
-		"0002_add_is_system_to_aliases.up.sql",
-		"0003_create_report_tables.up.sql",
-	}
-
-	for _, m := range migrations {
-		sql, err := os.ReadFile(filepath.Join(root, "migrations", m))
-		if err != nil {
-			t.Fatalf("read migration %s: %v", m, err)
-		}
-		if _, err := pool.Exec(ctx, string(sql)); err != nil {
-			t.Fatalf("apply migration %s: %v", m, err)
-		}
-	}
+	applyMigrations(t, ctx, pool)
 
 	// Seed domain, sender mailbox, INBOX
 	domainID := uuid.New()

services/protocols/internal/e2e/pop3_e2e_test.go

@@ -14,8 +14,8 @@ import (
 	"github.com/alexedwards/argon2id"
 	embeddedpostgres "github.com/fergusstrange/embedded-postgres"
 
-	appusecase "lambdamail/protocols/internal/application/usecase"
 	"lambdamail/protocols/internal/application/port"
+	appusecase "lambdamail/protocols/internal/application/usecase"
 	"lambdamail/protocols/internal/infrastructure/diskstorage"
 	"lambdamail/protocols/internal/infrastructure/postgres"
 	pop3presentation "lambdamail/protocols/internal/presentation/pop3"

services/protocols/internal/e2e/smtp_inbound_e2e_test.go

@@ -19,8 +19,8 @@ import (
 	"testing"
 	"time"
 
-	embeddedpostgres "github.com/fergusstrange/embedded-postgres"
 	gosmtp "github.com/emersion/go-smtp"
+	embeddedpostgres "github.com/fergusstrange/embedded-postgres"
 
 	"lambdamail/protocols/internal/application/usecase"
 	"lambdamail/protocols/internal/infrastructure/diskstorage"

services/protocols/internal/e2e/submission_e2e_test.go

@@ -0,0 +1,360 @@
+package e2e
+
+import (
+	"bufio"
+	"context"
+	"crypto/tls"
+	"encoding/base64"
+	"fmt"
+	"net"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/alexedwards/argon2id"
+	embeddedpostgres "github.com/fergusstrange/embedded-postgres"
+	"github.com/google/uuid"
+
+	appusecase "lambdamail/protocols/internal/application/usecase"
+	"lambdamail/protocols/internal/infrastructure/diskstorage"
+	"lambdamail/protocols/internal/infrastructure/dkim"
+	"lambdamail/protocols/internal/infrastructure/postgres"
+	"lambdamail/protocols/internal/infrastructure/vault"
+	smtppresentation "lambdamail/protocols/internal/presentation/smtp"
+
+	gosmtp "github.com/emersion/go-smtp"
+)
+
+// TestSubmissionEndToEnd covers the outbound half of PLAN.md section 6.2:
+// an authenticated client submits on the submission port, the message is
+// signed with both DKIM keys, queued, and then delivered by the worker to a
+// remote MX.
+func TestSubmissionEndToEnd(t *testing.T) {
+	if testing.Short() {
+		t.Skip("e2e test skipped in -short mode")
+	}
+	ctx := context.Background()
+
+	runtimeDir := t.TempDir()
+	pg := embeddedpostgres.NewDatabase(embeddedpostgres.DefaultConfig().
+		Port(54344).
+		RuntimePath(runtimeDir).
+		StartTimeout(120 * time.Second))
+	if err := pg.Start(); err != nil {
+		t.Fatalf("start embedded postgres: %v", err)
+	}
+	defer pg.Stop()
+
+	dbURL := "postgres://postgres:postgres@localhost:54344/postgres?sslmode=disable"
+	pool, err := postgres.NewPool(ctx, dbURL)
+	if err != nil {
+		t.Fatalf("connect pool: %v", err)
+	}
+	defer pool.Close()
+
+	applyMigrations(t, ctx, pool)
+
+	// ---------------------------------------------------------------- seed
+	const (
+		senderAddress = "sender@submission.test"
+		password      = "correct horse battery staple"
+	)
+
+	domainID, mailboxID, inboxID := uuid.New(), uuid.New(), uuid.New()
+	hash, err := argon2id.CreateHash(password, argon2id.DefaultParams)
+	if err != nil {
+		t.Fatalf("hash password: %v", err)
+	}
+
+	pool.Exec(ctx, `INSERT INTO domains (id, name, punycode_name) VALUES ($1, 'submission.test', 'submission.test')`, domainID)
+	pool.Exec(ctx, `INSERT INTO mailboxes (id, domain_id, local_part, email_address, password_hash, max_recipients_per_hour)
+		VALUES ($1, $2, 'sender', $3, $4, 5)`, mailboxID, domainID, senderAddress, hash)
+	pool.Exec(ctx, `INSERT INTO folders (id, mailbox_id, name, special_use) VALUES ($1, $2, 'INBOX', 'inbox')`, inboxID, mailboxID)
+
+	// ----------------------------------------------------------- provision
+	secretVault, err := vault.New("e2e-master-key")
+	if err != nil {
+		t.Fatalf("vault: %v", err)
+	}
+	dkimRepo := postgres.NewDkimRepository(pool, secretVault)
+
+	provisioner := appusecase.NewProvisionDkimKeysUseCase(dkimRepo, func(algorithm string) ([]byte, string, error) {
+		generated, err := dkim.Generate(algorithm)
+		if err != nil {
+			return nil, "", err
+		}
+		return generated.PrivateKeyPEM, generated.PublicKeyBase64, nil
+	})
+
+	keys, err := provisioner.Execute(ctx, "submission.test")
+	if err != nil {
+		t.Fatalf("provision DKIM keys: %v", err)
+	}
+	if keys.RsaPublicKey == "" || keys.Ed25519PublicKey == "" {
+		t.Fatal("provisioning produced no public keys for the DNS records")
+	}
+
+	// The private halves must not be readable from the table without the
+	// master key (PLAN.md section 9).
+	var storedCiphertext []byte
+	pool.QueryRow(ctx, `SELECT private_key_enc FROM dkim_keys WHERE algorithm = 'rsa2048'`).Scan(&storedCiphertext)
+	if strings.Contains(string(storedCiphertext), "PRIVATE KEY") {
+		t.Error("the DKIM private key was stored in the clear")
+	}
+
+	// ------------------------------------------------------------- wiring
+	blobs := diskstorage.NewLocalDiskBlobStorage(pool, t.TempDir())
+	blobReader := diskstorage.NewLocalDiskBlobReader(pool)
+	authRepo := postgres.NewAuthRepository(pool)
+	outboundRepo := postgres.NewOutboundRepository(pool)
+
+	submissionUC := appusecase.NewProcessOutboundEmailUseCase(authRepo, outboundRepo, blobs, dkim.NewSigner(dkimRepo))
+
+	certificate := selfSignedTLSCert(t)
+	server := gosmtp.NewServer(smtppresentation.NewSubmissionBackend(submissionUC))
+	server.Domain = "mail.submission.test"
+	server.MaxMessageBytes = 10 << 20
+	server.MaxRecipients = 10
+	server.AllowInsecureAuth = false
+	server.TLSConfig = &tls.Config{Certificates: []tls.Certificate{certificate}}
+
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("listen: %v", err)
+	}
+	defer ln.Close()
+	go server.Serve(ln)
+
+	// -------------------------------------------------- submit over STARTTLS
+	submitMessage(t, ln.Addr().String(), senderAddress, password, "rcpt@remote.test")
+
+	// The job must be queued against the sending mailbox.
+	var queued int
+	var destinationDomain string
+	pool.QueryRow(ctx, `SELECT COUNT(*), COALESCE(MAX(destination_domain), '') FROM outbound_jobs WHERE mailbox_id = $1`, mailboxID).
+		Scan(&queued, &destinationDomain)
+	if queued != 1 {
+		t.Fatalf("queued %d jobs, want 1", queued)
+	}
+	if destinationDomain != "remote.test" {
+		t.Errorf("destination domain = %q, want remote.test", destinationDomain)
+	}
+
+	// The stored message must carry both signatures.
+	var blobID uuid.UUID
+	pool.QueryRow(ctx, `SELECT blob_id FROM outbound_jobs WHERE mailbox_id = $1`, mailboxID).Scan(&blobID)
+	stored, err := blobReader.ReadByID(ctx, blobID)
+	if err != nil {
+		t.Fatalf("read stored message: %v", err)
+	}
+	if count := strings.Count(string(stored), "DKIM-Signature:"); count != 2 {
+		t.Errorf("stored message carries %d DKIM signatures, want 2 (RSA and Ed25519)", count)
+	}
+	if !strings.Contains(string(stored), "d=submission.test") {
+		t.Errorf("signatures do not claim the sending domain:\n%s", stored)
+	}
+
+	// --------------------------------------------------------- delivery
+	received := make(chan string, 1)
+	mxAddr := startCapturingMX(t, received)
+
+	worker := appusecase.NewOutboundWorkerUseCase(
+		outboundRepo, &staticMXResolver{addr: mxAddr}, blobReader, nil, nil, "mail.submission.test",
+	)
+	if _, err := worker.ProcessBatch(ctx, "worker1", 10); err != nil {
+		t.Fatalf("ProcessBatch: %v", err)
+	}
+
+	var status, tlsPolicy string
+	pool.QueryRow(ctx, `SELECT status, COALESCE(tls_policy_used, '') FROM outbound_jobs WHERE mailbox_id = $1`, mailboxID).
+		Scan(&status, &tlsPolicy)
+	if status != "DELIVERED" {
+		var lastError string
+		pool.QueryRow(ctx, `SELECT COALESCE(last_error, '') FROM outbound_jobs WHERE mailbox_id = $1`, mailboxID).Scan(&lastError)
+		t.Fatalf("status = %s, want DELIVERED (last error: %s)", status, lastError)
+	}
+	if tlsPolicy != "opportunistic" {
+		t.Errorf("tls_policy_used = %q, want opportunistic for a destination with no published policy", tlsPolicy)
+	}
+
+	select {
+	case delivered := <-received:
+		if !strings.Contains(delivered, "DKIM-Signature:") {
+			t.Error("the delivered message lost its signatures")
+		}
+	case <-time.After(5 * time.Second):
+		t.Fatal("the remote MX never received the message")
+	}
+
+	// ------------------------------------------------ per-mailbox send limit
+	// The mailbox allows five recipients an hour and has used one.
+	assertSubmissionRefused(t, ln.Addr().String(), senderAddress, password,
+		[]string{"a@remote.test", "b@remote.test", "c@remote.test", "d@remote.test", "e@remote.test"})
+
+	// An account may not send as somebody else.
+	assertSenderRefused(t, ln.Addr().String(), senderAddress, password, "ceo@submission.test")
+}
+
+// submitMessage performs a full EHLO/STARTTLS/AUTH/MAIL/RCPT/DATA exchange.
+func submitMessage(t *testing.T, addr, username, password, recipient string) {
+	t.Helper()
+
+	client, err := gosmtp.DialStartTLS(addr, &tls.Config{InsecureSkipVerify: true})
+	if err != nil {
+		t.Fatalf("dial submission over STARTTLS: %v", err)
+	}
+	defer client.Close()
+
+	if err := client.Auth(plainAuth(username, password)); err != nil {
+		t.Fatalf("AUTH: %v", err)
+	}
+	if err := client.Mail(username, nil); err != nil {
+		t.Fatalf("MAIL FROM: %v", err)
+	}
+	if err := client.Rcpt(recipient, nil); err != nil {
+		t.Fatalf("RCPT TO: %v", err)
+	}
+
+	w, err := client.Data()
+	if err != nil {
+		t.Fatalf("DATA: %v", err)
+	}
+	message := fmt.Sprintf("From: %s\r\nTo: %s\r\nSubject: e2e\r\nDate: Mon, 20 Jul 2026 10:00:00 +0000\r\nMessage-ID: <e2e@submission.test>\r\n\r\nhello\r\n", username, recipient)
+	if _, err := w.Write([]byte(message)); err != nil {
+		t.Fatalf("write DATA: %v", err)
+	}
+	if err := w.Close(); err != nil {
+		t.Fatalf("close DATA: %v", err)
+	}
+	client.Quit()
+}
+
+// assertSubmissionRefused checks that going past the hourly recipient budget
+// is refused with a temporary error rather than silently accepted.
+func assertSubmissionRefused(t *testing.T, addr, username, password string, recipients []string) {
+	t.Helper()
+
+	client, err := gosmtp.DialStartTLS(addr, &tls.Config{InsecureSkipVerify: true})
+	if err != nil {
+		t.Fatalf("dial: %v", err)
+	}
+	defer client.Close()
+
+	client.Auth(plainAuth(username, password))
+	client.Mail(username, nil)
+	for _, r := range recipients {
+		client.Rcpt(r, nil)
+	}
+
+	w, err := client.Data()
+	if err != nil {
+		// Some servers refuse at DATA issue time; either point is acceptable.
+		return
+	}
+	w.Write([]byte("From: x\r\n\r\nbody\r\n"))
+	if err := w.Close(); err == nil {
+		t.Error("submission past the hourly recipient limit was accepted")
+	} else if !strings.Contains(err.Error(), "451") {
+		t.Errorf("error = %v, want a 451 temporary refusal", err)
+	}
+}
+
+func assertSenderRefused(t *testing.T, addr, username, password, forgedSender string) {
+	t.Helper()
+
+	client, err := gosmtp.DialStartTLS(addr, &tls.Config{InsecureSkipVerify: true})
+	if err != nil {
+		t.Fatalf("dial: %v", err)
+	}
+	defer client.Close()
+
+	client.Auth(plainAuth(username, password))
+
+	if err := client.Mail(forgedSender, nil); err == nil {
+		t.Errorf("MAIL FROM %s was accepted for an account that does not own it", forgedSender)
+	}
+}
+
+// startCapturingMX accepts one message and hands its body back on a channel.
+func startCapturingMX(t *testing.T, received chan<- string) string {
+	t.Helper()
+
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("listen: %v", err)
+	}
+	t.Cleanup(func() { ln.Close() })
+
+	go func() {
+		for {
+			conn, err := ln.Accept()
+			if err != nil {
+				return
+			}
+			go func(c net.Conn) {
+				defer c.Close()
+				c.SetDeadline(time.Now().Add(10 * time.Second))
+				r := bufio.NewReader(c)
+				c.Write([]byte("220 capture.mx ESMTP\r\n"))
+
+				var body strings.Builder
+				for {
+					line, err := r.ReadString('\n')
+					if err != nil {
+						return
+					}
+					switch cmd := strings.ToUpper(strings.TrimSpace(line)); {
+					case strings.HasPrefix(cmd, "EHLO"), strings.HasPrefix(cmd, "HELO"):
+						c.Write([]byte("250 capture.mx\r\n"))
+					case cmd == "DATA":
+						c.Write([]byte("354 Send it\r\n"))
+						for {
+							dataLine, err := r.ReadString('\n')
+							if err != nil {
+								return
+							}
+							if strings.TrimSpace(dataLine) == "." {
+								break
+							}
+							body.WriteString(dataLine)
+						}
+						c.Write([]byte("250 2.0.0 Queued\r\n"))
+						select {
+						case received <- body.String():
+						default:
+						}
+					case cmd == "QUIT":
+						c.Write([]byte("221 Bye\r\n"))
+						return
+					default:
+						c.Write([]byte("250 Ok\r\n"))
+					}
+				}
+			}(conn)
+		}
+	}()
+
+	return ln.Addr().String()
+}
+
+// plainAuth builds a SASL PLAIN client without pulling in another dependency.
+type plainAuthClient struct {
+	username, password string
+	done               bool
+}
+
+func plainAuth(username, password string) *plainAuthClient {
+	return &plainAuthClient{username: username, password: password}
+}
+
+func (a *plainAuthClient) Start() (mech string, ir []byte, err error) {
+	return "PLAIN", []byte("\x00" + a.username + "\x00" + a.password), nil
+}
+
+func (a *plainAuthClient) Next(challenge []byte) ([]byte, error) {
+	if a.done {
+		return nil, fmt.Errorf("unexpected challenge %q", base64.StdEncoding.EncodeToString(challenge))
+	}
+	a.done = true
+	return nil, nil
+}

services/protocols/internal/infrastructure/cloudflare/cloudflare_adapter.go

@@ -5,240 +5,392 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"io"
 	"net/http"
 	"net/url"
+	"strconv"
+	"strings"
+	"time"
 
 	"lambdamail/protocols/internal/application/port"
 	"lambdamail/protocols/internal/domain/entity"
 )
 
+const (
+	// rateLimitMaxAttempts bounds the 429 retry loop so a throttled zone
+	// delays the reconcile instead of blocking it forever.
+	rateLimitMaxAttempts = 4
+	rateLimitMaxBackoff  = 30 * time.Second
+	recordsPerPage       = 100
+)
+
 type CloudflareAdapter struct {
-	apiToken string
-	baseURL  string
+	apiToken   string
+	baseURL    string
 	httpClient *http.Client
 }
 
 func NewCloudflareAdapter(apiToken string) *CloudflareAdapter {
 	return &CloudflareAdapter{
-		apiToken:   apiToken,
-		baseURL:    "https://api.cloudflare.com/client/v4",
-		httpClient: &http.Client{},
+		apiToken: apiToken,
+		baseURL:  "https://api.cloudflare.com/client/v4",
+		// Without a timeout a stalled API call would hold the reconcile - and
+		// on the periodic drift job, the goroutine - open indefinitely.
+		httpClient: &http.Client{Timeout: 30 * time.Second},
 	}
 }
 
+type cfError struct {
+	Message string `json:"message"`
+}
+
+type cfResultInfo struct {
+	Page       int `json:"page"`
+	TotalPages int `json:"total_pages"`
+}
+
 type cfZoneResponse struct {
 	Success bool `json:"success"`
 	Result  []struct {
 		ID   string `json:"id"`
 		Name string `json:"name"`
 	} `json:"result"`
-	Errors []struct {
-		Message string `json:"message"`
-	} `json:"errors"`
+	Errors []cfError `json:"errors"`
 }
 
 type cfRecord struct {
-	ID       string `json:"id,omitempty"`
-	Type     string `json:"type"`
-	Name     string `json:"name"`
-	Content  string `json:"content"`
-	TTL      int    `json:"ttl"`
-	Priority *int   `json:"priority,omitempty"`
-	Proxied  bool   `json:"proxied,omitempty"`
-	Comment  string `json:"comment,omitempty"`
+	ID      string `json:"id,omitempty"`
+	Type    string `json:"type"`
+	Name    string `json:"name"`
+	Content string `json:"content,omitempty"`
+	TTL     int    `json:"ttl"`
+	// Pointers so that "absent" and "explicitly false" stay distinguishable:
+	// Cloudflare applies its own default for an omitted proxied flag, and a
+	// proxied mail host silently breaks SMTP (PLAN.md section 7.1).
+	Priority *int  `json:"priority,omitempty"`
+	Proxied  *bool `json:"proxied,omitempty"`
+	// Data carries the structured form Cloudflare requires for SRV and TLSA;
+	// those types reject a flat content string.
+	Data    map[string]any `json:"data,omitempty"`
+	Comment string         `json:"comment,omitempty"`
 }
 
 type cfRecordResponse struct {
-	Success bool       `json:"success"`
-	Result  []cfRecord `json:"result"`
-	Errors  []struct {
-		Message string `json:"message"`
-	} `json:"errors"`
+	Success    bool         `json:"success"`
+	Result     []cfRecord   `json:"result"`
+	ResultInfo cfResultInfo `json:"result_info"`
+	Errors     []cfError    `json:"errors"`
 }
 
 type cfSingleRecordResponse struct {
-	Success bool     `json:"success"`
-	Result  cfRecord `json:"result"`
-	Errors  []struct {
-		Message string `json:"message"`
-	} `json:"errors"`
+	Success bool      `json:"success"`
+	Result  cfRecord  `json:"result"`
+	Errors  []cfError `json:"errors"`
 }
 
 func (a *CloudflareAdapter) GetZoneID(ctx context.Context, domainName string) (string, error) {
 	reqURL := fmt.Sprintf("%s/zones?name=%s", a.baseURL, url.QueryEscape(domainName))
-	req, err := http.NewRequestWithContext(ctx, http.MethodGet, reqURL, nil)
-	if err != nil {
-		return "", err
-	}
-	a.setHeaders(req)
-
-	resp, err := a.httpClient.Do(req)
-	if err != nil {
-		return "", err
-	}
-	defer resp.Body.Close()
 
 	var data cfZoneResponse
-	if err := json.NewDecoder(resp.Body).Decode(&data); err != nil {
-		return "", fmt.Errorf("decode json: %w", err)
+	if err := a.doJSON(ctx, http.MethodGet, reqURL, nil, &data, func() []cfError { return data.Errors }); err != nil {
+		return "", err
 	}
 
 	if !data.Success || len(data.Result) == 0 {
-		errMsg := "zone not found"
-		if len(data.Errors) > 0 {
-			errMsg = data.Errors[0].Message
-		}
-		return "", fmt.Errorf("cloudflare API error: %s", errMsg)
+		return "", fmt.Errorf("cloudflare: zone %q not found or token lacks Zone:Read on it", domainName)
 	}
 
 	return data.Result[0].ID, nil
 }
 
 func (a *CloudflareAdapter) ListRecords(ctx context.Context, zoneID string) ([]entity.DnsRecord, error) {
-	reqURL := fmt.Sprintf("%s/zones/%s/dns_records?per_page=100", a.baseURL, zoneID)
-	req, err := http.NewRequestWithContext(ctx, http.MethodGet, reqURL, nil)
-	if err != nil {
-		return nil, err
-	}
-	a.setHeaders(req)
-
-	resp, err := a.httpClient.Do(req)
-	if err != nil {
-		return nil, err
-	}
-	defer resp.Body.Close()
-
-	var data cfRecordResponse
-	if err := json.NewDecoder(resp.Body).Decode(&data); err != nil {
-		return nil, fmt.Errorf("decode json: %w", err)
-	}
-
-	if !data.Success {
-		return nil, fmt.Errorf("cloudflare API error listing records")
-	}
-
 	var out []entity.DnsRecord
-	for _, r := range data.Result {
-		out = append(out, entity.DnsRecord{
-			ID:       r.ID,
-			Type:     r.Type,
-			Name:     r.Name,
-			Value:    r.Content,
-			TTL:      r.TTL,
-			Priority: r.Priority,
-			Proxied:  r.Proxied,
-			Comment:  r.Comment,
-		})
+
+	for page := 1; ; page++ {
+		reqURL := fmt.Sprintf("%s/zones/%s/dns_records?per_page=%d&page=%d", a.baseURL, zoneID, recordsPerPage, page)
+
+		var data cfRecordResponse
+		if err := a.doJSON(ctx, http.MethodGet, reqURL, nil, &data, func() []cfError { return data.Errors }); err != nil {
+			return nil, err
+		}
+		if !data.Success {
+			return nil, fmt.Errorf("cloudflare: listing records for zone %s failed", zoneID)
+		}
+
+		for _, r := range data.Result {
+			rec := entity.DnsRecord{
+				ID:       r.ID,
+				Type:     r.Type,
+				Name:     r.Name,
+				Value:    r.Content,
+				TTL:      r.TTL,
+				Priority: r.Priority,
+				Comment:  r.Comment,
+			}
+			if r.Proxied != nil {
+				rec.Proxied = *r.Proxied
+			}
+			// Cloudflare returns SRV and TLSA with content already rendered,
+			// but older zones and some responses only populate data; fall back
+			// to it so a structured record is not seen as an empty value and
+			// rewritten on every reconcile.
+			if rec.Value == "" && len(r.Data) > 0 {
+				rec.Value = renderStructuredValue(r.Type, r.Data)
+			}
+			out = append(out, rec)
+		}
+
+		// Zones larger than one page would otherwise look like they are
+		// missing records, and the reconciler would try to re-create them.
+		if data.ResultInfo.TotalPages <= page || len(data.Result) == 0 {
+			break
+		}
 	}
+
 	return out, nil
 }
 
 func (a *CloudflareAdapter) CreateRecord(ctx context.Context, zoneID string, record entity.DnsRecord) error {
 	reqURL := fmt.Sprintf("%s/zones/%s/dns_records", a.baseURL, zoneID)
-	cfBody := cfRecord{
-		Type:     record.Type,
-		Name:     record.Name,
-		Content:  record.Value,
-		TTL:      record.TTL,
-		Priority: record.Priority,
-		Proxied:  record.Proxied,
-		Comment:  record.Comment,
-	}
-
-	payload, err := json.Marshal(cfBody)
-	if err != nil {
-		return err
-	}
-
-	req, err := http.NewRequestWithContext(ctx, http.MethodPost, reqURL, bytes.NewBuffer(payload))
-	if err != nil {
-		return err
-	}
-	a.setHeaders(req)
-
-	resp, err := a.httpClient.Do(req)
-	if err != nil {
-		return err
-	}
-	defer resp.Body.Close()
 
 	var data cfSingleRecordResponse
-	if err := json.NewDecoder(resp.Body).Decode(&data); err != nil {
-		return err
+	if err := a.doJSON(ctx, http.MethodPost, reqURL, toCfRecord(record), &data, func() []cfError { return data.Errors }); err != nil {
+		return fmt.Errorf("create %s %s: %w", record.Type, record.Name, err)
 	}
-
 	if !data.Success {
-		errMsg := "create record failed"
-		if len(data.Errors) > 0 {
-			errMsg = data.Errors[0].Message
-		}
-		return fmt.Errorf("cloudflare API error: %s", errMsg)
+		return fmt.Errorf("cloudflare: create %s %s failed", record.Type, record.Name)
 	}
-
 	return nil
 }
 
 func (a *CloudflareAdapter) UpdateRecord(ctx context.Context, zoneID string, record entity.DnsRecord) error {
 	reqURL := fmt.Sprintf("%s/zones/%s/dns_records/%s", a.baseURL, zoneID, record.ID)
-	cfBody := cfRecord{
-		Type:     record.Type,
-		Name:     record.Name,
-		Content:  record.Value,
-		TTL:      record.TTL,
-		Priority: record.Priority,
-		Proxied:  record.Proxied,
-		Comment:  record.Comment,
-	}
-
-	payload, err := json.Marshal(cfBody)
-	if err != nil {
-		return err
-	}
-
-	req, err := http.NewRequestWithContext(ctx, http.MethodPut, reqURL, bytes.NewBuffer(payload))
-	if err != nil {
-		return err
-	}
-	a.setHeaders(req)
-
-	resp, err := a.httpClient.Do(req)
-	if err != nil {
-		return err
-	}
-	defer resp.Body.Close()
 
 	var data cfSingleRecordResponse
-	if err := json.NewDecoder(resp.Body).Decode(&data); err != nil {
-		return err
+	if err := a.doJSON(ctx, http.MethodPut, reqURL, toCfRecord(record), &data, func() []cfError { return data.Errors }); err != nil {
+		return fmt.Errorf("update %s %s: %w", record.Type, record.Name, err)
 	}
-
 	if !data.Success {
-		return fmt.Errorf("cloudflare API error updating record")
+		return fmt.Errorf("cloudflare: update %s %s failed", record.Type, record.Name)
 	}
-
 	return nil
 }
 
 func (a *CloudflareAdapter) DeleteRecord(ctx context.Context, zoneID string, recordID string) error {
 	reqURL := fmt.Sprintf("%s/zones/%s/dns_records/%s", a.baseURL, zoneID, recordID)
-	req, err := http.NewRequestWithContext(ctx, http.MethodDelete, reqURL, nil)
-	if err != nil {
-		return err
-	}
-	a.setHeaders(req)
 
-	resp, err := a.httpClient.Do(req)
-	if err != nil {
-		return err
+	var data cfSingleRecordResponse
+	if err := a.doJSON(ctx, http.MethodDelete, reqURL, nil, &data, func() []cfError { return data.Errors }); err != nil {
+		return fmt.Errorf("delete record %s: %w", recordID, err)
+	}
+	if !data.Success {
+		return fmt.Errorf("cloudflare: delete record %s failed", recordID)
+	}
+	return nil
+}
+
+// toCfRecord maps a desired record onto the API payload. The proxied flag is
+// only meaningful for the record types Cloudflare can proxy; sending it for a
+// TXT or MX record is rejected.
+func toCfRecord(record entity.DnsRecord) cfRecord {
+	body := cfRecord{
+		ID:       record.ID,
+		Type:     record.Type,
+		Name:     record.Name,
+		Content:  record.Value,
+		TTL:      record.TTL,
+		Priority: record.Priority,
+		Comment:  record.Comment,
+	}
+
+	switch strings.ToUpper(record.Type) {
+	case "A", "AAAA", "CNAME":
+		proxied := record.Proxied
+		body.Proxied = &proxied
+
+	case "SRV", "TLSA":
+		// These types are rejected with a flat content string; the API wants
+		// the components broken out.
+		if data := structuredData(record); data != nil {
+			body.Data = data
+			body.Content = ""
+			body.Priority = nil
+		}
+	}
+
+	return body
+}
+
+// structuredData splits an SRV or TLSA record value into the field map the
+// Cloudflare API expects. It returns nil when the value is not in the
+// canonical presentation form, letting the caller fall back to content.
+func structuredData(record entity.DnsRecord) map[string]any {
+	fields := strings.Fields(record.Value)
+
+	switch strings.ToUpper(record.Type) {
+	case "SRV":
+		// Presentation form: "<priority> <weight> <port> <target>".
+		if len(fields) != 4 {
+			return nil
+		}
+		priority, err1 := strconv.Atoi(fields[0])
+		weight, err2 := strconv.Atoi(fields[1])
+		port, err3 := strconv.Atoi(fields[2])
+		if err1 != nil || err2 != nil || err3 != nil {
+			return nil
+		}
+		return map[string]any{
+			"priority": priority,
+			"weight":   weight,
+			"port":     port,
+			"target":   strings.TrimSuffix(fields[3], "."),
+		}
+
+	case "TLSA":
+		// Presentation form: "<usage> <selector> <matching type> <data>".
+		if len(fields) != 4 {
+			return nil
+		}
+		usage, err1 := strconv.Atoi(fields[0])
+		selector, err2 := strconv.Atoi(fields[1])
+		matchingType, err3 := strconv.Atoi(fields[2])
+		if err1 != nil || err2 != nil || err3 != nil {
+			return nil
+		}
+		return map[string]any{
+			"usage":         usage,
+			"selector":      selector,
+			"matching_type": matchingType,
+			"certificate":   fields[3],
+		}
 	}
-	defer resp.Body.Close()
 
 	return nil
 }
 
-func (a *CloudflareAdapter) setHeaders(req *http.Request) {
-	req.Header.Set("Authorization", "Bearer "+a.apiToken)
-	req.Header.Set("Content-Type", "application/json")
+// renderStructuredValue is the inverse of structuredData: it rebuilds the
+// presentation form so the reconciler can compare a published record against
+// the desired one.
+func renderStructuredValue(recordType string, data map[string]any) string {
+	number := func(key string) string {
+		switch v := data[key].(type) {
+		case float64: // JSON numbers decode as float64
+			return strconv.Itoa(int(v))
+		case string:
+			return v
+		default:
+			return ""
+		}
+	}
+	text := func(key string) string {
+		if v, ok := data[key].(string); ok {
+			return strings.TrimSuffix(v, ".")
+		}
+		return ""
+	}
+
+	switch strings.ToUpper(recordType) {
+	case "SRV":
+		return strings.Join([]string{number("priority"), number("weight"), number("port"), text("target")}, " ")
+	case "TLSA":
+		return strings.Join([]string{number("usage"), number("selector"), number("matching_type"), text("certificate")}, " ")
+	default:
+		return ""
+	}
+}
+
+// doJSON performs one API call, retrying while Cloudflare reports 429 and
+// honouring Retry-After (PLAN.md section 7.5). It fails on any non-2xx status
+// rather than handing a decoder an error page.
+func (a *CloudflareAdapter) doJSON(ctx context.Context, method, reqURL string, body any, out any, errsOf func() []cfError) error {
+	var payload []byte
+	if body != nil {
+		var err error
+		if payload, err = json.Marshal(body); err != nil {
+			return fmt.Errorf("encode request body: %w", err)
+		}
+	}
+
+	backoff := time.Second
+
+	for attempt := 1; ; attempt++ {
+		var reader io.Reader
+		if payload != nil {
+			reader = bytes.NewReader(payload)
+		}
+
+		req, err := http.NewRequestWithContext(ctx, method, reqURL, reader)
+		if err != nil {
+			return err
+		}
+		req.Header.Set("Authorization", "Bearer "+a.apiToken)
+		req.Header.Set("Content-Type", "application/json")
+
+		resp, err := a.httpClient.Do(req)
+		if err != nil {
+			return err
+		}
+
+		if resp.StatusCode == http.StatusTooManyRequests && attempt < rateLimitMaxAttempts {
+			wait := retryAfter(resp.Header.Get("Retry-After"), backoff)
+			resp.Body.Close()
+			backoff = min(backoff*2, rateLimitMaxBackoff)
+
+			select {
+			case <-ctx.Done():
+				return ctx.Err()
+			case <-time.After(wait):
+			}
+			continue
+		}
+
+		respBody, readErr := io.ReadAll(resp.Body)
+		resp.Body.Close()
+		if readErr != nil {
+			return fmt.Errorf("read response body: %w", readErr)
+		}
+
+		// Decode first so an error envelope can be quoted back to the operator,
+		// then judge the status. Cloudflare returns its envelope on 4xx too.
+		decodeErr := json.Unmarshal(respBody, out)
+
+		if resp.StatusCode < 200 || resp.StatusCode >= 300 {
+			return fmt.Errorf("cloudflare API returned HTTP %d: %s", resp.StatusCode, describeErrors(errsOf(), respBody))
+		}
+		if decodeErr != nil {
+			return fmt.Errorf("decode json: %w", decodeErr)
+		}
+		return nil
+	}
+}
+
+func describeErrors(errs []cfError, raw []byte) string {
+	if len(errs) > 0 {
+		messages := make([]string, 0, len(errs))
+		for _, e := range errs {
+			messages = append(messages, e.Message)
+		}
+		return strings.Join(messages, "; ")
+	}
+	const maxRaw = 200
+	if len(raw) > maxRaw {
+		raw = raw[:maxRaw]
+	}
+	return strings.TrimSpace(string(raw))
+}
+
+// retryAfter reads the header as delta-seconds (RFC 9110 section 10.2.3),
+// falling back to the caller's exponential backoff when it is absent or
+// unparseable.
+func retryAfter(header string, fallback time.Duration) time.Duration {
+	if header == "" {
+		return fallback
+	}
+	seconds, err := strconv.Atoi(strings.TrimSpace(header))
+	if err != nil || seconds < 0 {
+		return fallback
+	}
+	return time.Duration(seconds) * time.Second
 }
 
 // Ensure port interface compliance

services/protocols/internal/infrastructure/cloudflare/cloudflare_hardening_test.go

@@ -0,0 +1,237 @@
+package cloudflare
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"lambdamail/protocols/internal/domain/entity"
+)
+
+// A proxied A record for the mail host makes Cloudflare answer with its own
+// anycast addresses, which do not speak SMTP - the domain stops receiving mail.
+// PLAN.md section 7.1 requires proxied=false, so the flag must be sent
+// explicitly rather than left to the zone default.
+func TestCloudflareAdapter_CreateRecord_SendsProxiedFalseExplicitly(t *testing.T) {
+	var body map[string]interface{}
+
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		json.NewDecoder(r.Body).Decode(&body)
+		json.NewEncoder(w).Encode(map[string]interface{}{"success": true, "result": map[string]interface{}{"id": "rec_1"}})
+	}))
+	defer ts.Close()
+
+	adapter := NewCloudflareAdapter("token")
+	adapter.baseURL = ts.URL
+
+	err := adapter.CreateRecord(context.Background(), "zone1", entity.DnsRecord{
+		Type: "A", Name: "mail.example.test", Value: "192.0.2.1", TTL: 1, Proxied: false,
+	})
+	if err != nil {
+		t.Fatalf("CreateRecord: %v", err)
+	}
+
+	proxied, present := body["proxied"]
+	if !present {
+		t.Fatal("proxied flag was omitted from the request; Cloudflare would fall back to the zone default")
+	}
+	if proxied != false {
+		t.Errorf("proxied = %v, want false", proxied)
+	}
+}
+
+// An HTTP-level failure carries no Cloudflare envelope, so a decoder-only
+// check reports a confusing JSON error - or worse, silently succeeds.
+func TestCloudflareAdapter_ReportsHttpErrorStatus(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusForbidden)
+		w.Write([]byte(`{"success":false,"errors":[{"message":"Insufficient permissions"}]}`))
+	}))
+	defer ts.Close()
+
+	adapter := NewCloudflareAdapter("token")
+	adapter.baseURL = ts.URL
+
+	_, err := adapter.GetZoneID(context.Background(), "example.test")
+	if err == nil {
+		t.Fatal("expected an error for HTTP 403")
+	}
+	if !strings.Contains(err.Error(), "Insufficient permissions") {
+		t.Errorf("error should surface the API message, got: %v", err)
+	}
+}
+
+// PLAN.md section 7.5 lists the record listing as paginated. Stopping at the
+// first page makes the reconciler believe records are missing and try to
+// re-create them, which the API then rejects.
+func TestCloudflareAdapter_ListRecords_FollowsPagination(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		page := r.URL.Query().Get("page")
+		if page == "" || page == "1" {
+			json.NewEncoder(w).Encode(map[string]interface{}{
+				"success": true,
+				"result": []map[string]interface{}{
+					{"id": "rec_1", "type": "A", "name": "a.example.test", "content": "192.0.2.1"},
+				},
+				"result_info": map[string]interface{}{"page": 1, "total_pages": 2},
+			})
+			return
+		}
+		json.NewEncoder(w).Encode(map[string]interface{}{
+			"success": true,
+			"result": []map[string]interface{}{
+				{"id": "rec_2", "type": "A", "name": "b.example.test", "content": "192.0.2.2"},
+			},
+			"result_info": map[string]interface{}{"page": 2, "total_pages": 2},
+		})
+	}))
+	defer ts.Close()
+
+	adapter := NewCloudflareAdapter("token")
+	adapter.baseURL = ts.URL
+
+	records, err := adapter.ListRecords(context.Background(), "zone1")
+	if err != nil {
+		t.Fatalf("ListRecords: %v", err)
+	}
+	if len(records) != 2 {
+		t.Fatalf("got %d records, want 2 across both pages", len(records))
+	}
+}
+
+// PLAN.md section 7.5 requires retrying 429 while honouring Retry-After.
+func TestCloudflareAdapter_RetriesOnRateLimit(t *testing.T) {
+	var calls int
+
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		calls++
+		if calls == 1 {
+			w.Header().Set("Retry-After", "0")
+			w.WriteHeader(http.StatusTooManyRequests)
+			return
+		}
+		json.NewEncoder(w).Encode(map[string]interface{}{
+			"success": true,
+			"result":  []map[string]interface{}{{"id": "zone_1", "name": "example.test"}},
+		})
+	}))
+	defer ts.Close()
+
+	adapter := NewCloudflareAdapter("token")
+	adapter.baseURL = ts.URL
+
+	zoneID, err := adapter.GetZoneID(context.Background(), "example.test")
+	if err != nil {
+		t.Fatalf("GetZoneID: %v", err)
+	}
+	if zoneID != "zone_1" {
+		t.Errorf("zoneID = %q, want zone_1", zoneID)
+	}
+	if calls != 2 {
+		t.Errorf("made %d calls, want 2 (one rate limited, one retried)", calls)
+	}
+}
+
+// A failed delete that reports success would silently leave stale records in
+// the zone.
+func TestCloudflareAdapter_DeleteRecord_ReportsFailure(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusNotFound)
+		w.Write([]byte(`{"success":false,"errors":[{"message":"Record not found"}]}`))
+	}))
+	defer ts.Close()
+
+	adapter := NewCloudflareAdapter("token")
+	adapter.baseURL = ts.URL
+
+	if err := adapter.DeleteRecord(context.Background(), "zone1", "rec_missing"); err == nil {
+		t.Fatal("expected an error when the delete fails")
+	}
+}
+
+// Cloudflare rejects SRV and TLSA records submitted as a flat content string;
+// they must be broken into the structured data object.
+func TestCloudflareAdapter_SendsStructuredDataForSrvAndTlsa(t *testing.T) {
+	cases := []struct {
+		name     string
+		record   entity.DnsRecord
+		expected map[string]interface{}
+	}{
+		{
+			name:   "SRV",
+			record: entity.DnsRecord{Type: "SRV", Name: "_imaps._tcp.example.test", Value: "0 1 993 mail.example.test", TTL: 1},
+			expected: map[string]interface{}{
+				"priority": float64(0), "weight": float64(1), "port": float64(993), "target": "mail.example.test",
+			},
+		},
+		{
+			name:   "TLSA",
+			record: entity.DnsRecord{Type: "TLSA", Name: "_25._tcp.mail.example.test", Value: "3 1 1 " + strings.Repeat("ab", 32), TTL: 1},
+			expected: map[string]interface{}{
+				"usage": float64(3), "selector": float64(1), "matching_type": float64(1), "certificate": strings.Repeat("ab", 32),
+			},
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			var body map[string]interface{}
+			ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				json.NewDecoder(r.Body).Decode(&body)
+				json.NewEncoder(w).Encode(map[string]interface{}{"success": true, "result": map[string]interface{}{"id": "rec_1"}})
+			}))
+			defer ts.Close()
+
+			adapter := NewCloudflareAdapter("token")
+			adapter.baseURL = ts.URL
+
+			if err := adapter.CreateRecord(context.Background(), "zone1", tc.record); err != nil {
+				t.Fatalf("CreateRecord: %v", err)
+			}
+
+			data, ok := body["data"].(map[string]interface{})
+			if !ok {
+				t.Fatalf("no structured data object sent; body = %v", body)
+			}
+			for key, want := range tc.expected {
+				if data[key] != want {
+					t.Errorf("data[%q] = %v, want %v", key, data[key], want)
+				}
+			}
+			if content, present := body["content"]; present && content != "" {
+				t.Errorf("content was sent alongside data: %v", content)
+			}
+		})
+	}
+}
+
+// A record returned with only a data object must round-trip back to the
+// presentation form, or the reconciler sees an empty value and rewrites it on
+// every run.
+func TestCloudflareAdapter_ListRecords_RendersStructuredValues(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		json.NewEncoder(w).Encode(map[string]interface{}{
+			"success": true,
+			"result": []map[string]interface{}{{
+				"id": "rec_1", "type": "SRV", "name": "_imaps._tcp.example.test",
+				"data": map[string]interface{}{"priority": 0, "weight": 1, "port": 993, "target": "mail.example.test"},
+			}},
+			"result_info": map[string]interface{}{"page": 1, "total_pages": 1},
+		})
+	}))
+	defer ts.Close()
+
+	adapter := NewCloudflareAdapter("token")
+	adapter.baseURL = ts.URL
+
+	records, err := adapter.ListRecords(context.Background(), "zone1")
+	if err != nil {
+		t.Fatalf("ListRecords: %v", err)
+	}
+	if len(records) != 1 || records[0].Value != "0 1 993 mail.example.test" {
+		t.Errorf("value = %q, want the rendered presentation form", records[0].Value)
+	}
+}

services/protocols/internal/infrastructure/postgres/auth_repository.go

@@ -21,7 +21,7 @@ func NewAuthRepository(pool *pgxpool.Pool) *AuthRepository {
 
 func (r *AuthRepository) FindByAddress(ctx context.Context, address string) (*port.MailboxAuth, error) {
 	row := r.pool.QueryRow(ctx, `
-		SELECT m.id, m.password_hash
+		SELECT m.id, m.password_hash, m.email_address, d.name, m.max_recipients_per_hour
 		FROM mailboxes m
 		JOIN domains d ON d.id = m.domain_id
 		WHERE m.email_address = $1
@@ -31,7 +31,7 @@ func (r *AuthRepository) FindByAddress(ctx context.Context, address string) (*po
 
 	var rec port.MailboxAuth
 	var id uuid.UUID
-	if err := row.Scan(&id, &rec.PasswordHash); err != nil {
+	if err := row.Scan(&id, &rec.PasswordHash, &rec.EmailAddress, &rec.DomainName, &rec.MaxRecipientsPerHour); err != nil {
 		if err == pgx.ErrNoRows {
 			return nil, nil
 		}

services/protocols/internal/infrastructure/postgres/outbound_repository.go

@@ -3,6 +3,9 @@ package postgres
 import (
 	"context"
 	"fmt"
+	"time"
+
+	"github.com/google/uuid"
 
 	"github.com/jackc/pgx/v5/pgxpool"
 
@@ -37,8 +40,13 @@ func (r *OutboundRepository) FetchNextReady(ctx context.Context, workerID string
 	rows, err := r.pool.Query(ctx, `
 		WITH ready_jobs AS (
 			SELECT id FROM outbound_jobs
-			WHERE status IN ('QUEUED', 'DEFERRED')
-			  AND next_attempt_at <= NOW()
+			WHERE (
+			        (status IN ('QUEUED', 'DEFERRED') AND next_attempt_at <= NOW())
+			        -- Reclaim jobs whose worker died mid-delivery. Without this
+			        -- they stay SENDING forever and the message is silently
+			        -- lost, which contradicts ADR-002's durability guarantee.
+			     OR (status = 'SENDING' AND locked_until IS NOT NULL AND locked_until <= NOW())
+			      )
 			ORDER BY next_attempt_at ASC
 			LIMIT $2
 			FOR UPDATE SKIP LOCKED
@@ -90,6 +98,22 @@ func (r *OutboundRepository) FetchNextReady(ctx context.Context, workerID string
 	return jobs, nil
 }
 
+// CountRecipientsSince counts queued recipients, not messages: one message to
+// fifty addresses is fifty recipients against the limit, which is the number
+// that matters for abuse.
+func (r *OutboundRepository) CountRecipientsSince(ctx context.Context, mailboxID uuid.UUID, since time.Time) (int, error) {
+	var count int
+	err := r.pool.QueryRow(ctx, `
+		SELECT COUNT(*) FROM outbound_jobs
+		WHERE mailbox_id = $1 AND created_at >= $2
+	`, mailboxID, since).Scan(&count)
+
+	if err != nil {
+		return 0, fmt.Errorf("count recent recipients for mailbox %s: %w", mailboxID, err)
+	}
+	return count, nil
+}
+
 func (r *OutboundRepository) UpdateJob(ctx context.Context, job *entity.OutboundJob) error {
 	_, err := r.pool.Exec(ctx, `
 		UPDATE outbound_jobs

services/protocols/internal/infrastructure/rspamd/rspamd_adapter.go

@@ -7,15 +7,16 @@ import (
 	"fmt"
 	"net/http"
 	"strings"
+	"time"
 
 	"lambdamail/protocols/internal/application/port"
 	"lambdamail/protocols/internal/domain/valueobject"
 )
 
 type RspamdResponse struct {
-	Action        string                         `json:"action"`
-	Score         float64                        `json:"score"`
-	RequiredScore float64                        `json:"required_score"`
+	Action        string                            `json:"action"`
+	Score         float64                           `json:"score"`
+	RequiredScore float64                           `json:"required_score"`
 	Symbols       map[string]map[string]interface{} `json:"symbols"`
 }
 
@@ -29,8 +30,11 @@ func NewRspamdAdapter(baseURL string) *RspamdAdapter {
 		baseURL = "http://localhost:11333"
 	}
 	return &RspamdAdapter{
-		baseURL:    strings.TrimSuffix(baseURL, "/"),
-		httpClient: &http.Client{},
+		baseURL: strings.TrimSuffix(baseURL, "/"),
+		// A scan sits in the middle of an open SMTP transaction, so an
+		// unbounded request would pin the session (and the sender's socket)
+		// until the peer gives up.
+		httpClient: &http.Client{Timeout: 30 * time.Second},
 	}
 }
 
@@ -86,7 +90,9 @@ func (a *RspamdAdapter) Scan(ctx context.Context, input port.ScanInput) (*valueo
 	switch parsed.Action {
 	case "reject":
 		res.Verdict = valueobject.ScanVerdictSpamReject
-	case "greylist":
+	// "soft reject" is Rspamd asking the sender to retry later (rate limit or
+	// transient policy); like a greylist it maps to a 4xx, never to acceptance.
+	case "greylist", "soft reject":
 		res.Verdict = valueobject.ScanVerdictGreylist
 	case "add header", "rewrite subject":
 		res.Verdict = valueobject.ScanVerdictSpamJunk

services/protocols/internal/infrastructure/rspamd/rspamd_adapter_test.go

@@ -18,7 +18,12 @@ func TestRspamdAdapter_Scan_MapsActions(t *testing.T) {
 	}{
 		{"no action", valueobject.ScanVerdictClean},
 		{"add header", valueobject.ScanVerdictSpamJunk},
+		{"rewrite subject", valueobject.ScanVerdictSpamJunk},
 		{"greylist", valueobject.ScanVerdictGreylist},
+		// Rspamd's "soft reject" asks the sender to come back later (rate
+		// limit, transient policy). Treating it as clean would accept mail
+		// the filter explicitly refused to accept yet.
+		{"soft reject", valueobject.ScanVerdictGreylist},
 		{"reject", valueobject.ScanVerdictSpamReject},
 	}
 

services/protocols/internal/presentation/http/router.go

@@ -3,6 +3,7 @@ package httppresentation
 import (
 	"fmt"
 	"io"
+	"net"
 	"net/http"
 	"strings"
 	"time"
@@ -11,10 +12,16 @@ import (
 	"lambdamail/protocols/internal/domain/valueobject"
 )
 
+// mtaStsMaxAge is the policy lifetime advertised to senders. RFC 8461
+// recommends a value in the order of weeks so that an attacker cannot strip
+// the policy by making the endpoint unreachable.
+const mtaStsMaxAge = 604800 // 7 days
+
 type Router struct {
 	mux           *http.ServeMux
 	reportUseCase *appusecase.IngestReportsUseCase
 	pingFunc      func() error
+	mtaStsMode    valueobject.MtaStsMode
 }
 
 func NewRouter(reportUseCase *appusecase.IngestReportsUseCase, pingFunc func() error) *Router {
@@ -22,11 +29,24 @@ func NewRouter(reportUseCase *appusecase.IngestReportsUseCase, pingFunc func() e
 		mux:           http.NewServeMux(),
 		reportUseCase: reportUseCase,
 		pingFunc:      pingFunc,
+		// PLAN.md section 5 ramps MTA-STS from testing to enforce. Starting at
+		// enforce means any TLS misconfiguration silently blackholes inbound
+		// mail from every sender that honours the policy, with no way to tell
+		// from this side - so the safe mode is the default and the operator
+		// promotes it once TLS-RPT reports come back clean.
+		mtaStsMode: valueobject.MtaStsModeTesting,
 	}
 	r.registerRoutes()
 	return r
 }
 
+// SetMtaStsMode selects the mode advertised in the served policy. Callers
+// should promote to enforce only after TLS-RPT confirms senders can negotiate
+// TLS against the published MX.
+func (r *Router) SetMtaStsMode(mode valueobject.MtaStsMode) {
+	r.mtaStsMode = mode
+}
+
 func (r *Router) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 	r.mux.ServeHTTP(w, req)
 }
@@ -57,19 +77,23 @@ func (r *Router) handleMtaSts(w http.ResponseWriter, req *http.Request) {
 	host := extractHost(req.Host)
 	domainName := strings.TrimPrefix(host, "mta-sts.")
 
-	policy := valueobject.NewMtaStsPolicy(valueobject.MtaStsModeEnforce, []string{fmt.Sprintf("mail.%s", domainName)}, 604800)
+	policy := valueobject.NewMtaStsPolicy(r.mtaStsMode, []string{fmt.Sprintf("mail.%s", domainName)}, mtaStsMaxAge)
 
 	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
-	w.Header().Set("Cache-Control", "public, max-age=86400")
+	// Kept in step with max_age so an HTTP cache cannot outlive the policy it
+	// is caching.
+	w.Header().Set("Cache-Control", fmt.Sprintf("public, max-age=%d", mtaStsMaxAge))
 	w.WriteHeader(http.StatusOK)
 	w.Write([]byte(policy.Format()))
 }
 
 func (r *Router) handleSecurityTxt(w http.ResponseWriter, req *http.Request) {
-	host := extractHost(req.Host)
+	// The contact must be a real mailbox on the mail domain, not on whichever
+	// service hostname the request happened to arrive at.
+	domainName := baseDomain(extractHost(req.Host))
 	expires := time.Now().AddDate(1, 0, 0).Format(time.RFC3339)
 
-	content := fmt.Sprintf("Contact: mailto:security@%s\r\nExpires: %s\r\nPreferred-Languages: en, pt-BR, es\r\n", host, expires)
+	content := fmt.Sprintf("Contact: mailto:security@%s\r\nExpires: %s\r\nPreferred-Languages: en, pt-BR, es\r\n", domainName, expires)
 
 	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
 	w.WriteHeader(http.StatusOK)
@@ -144,12 +168,27 @@ func (r *Router) handleTlsRptIngest(w http.ResponseWriter, req *http.Request) {
 	w.Write([]byte(`{"status":"ok"}`))
 }
 
+// extractHost strips the optional port from a Host header, handling the
+// bracketed IPv6 literal form as well.
 func extractHost(hostHeader string) string {
-	if h, _, err := strings.Cut(hostHeader, ":"); err && h != "" {
-		return h
-	}
 	if hostHeader == "" {
 		return "example.test"
 	}
-	return hostHeader
+	if host, _, err := net.SplitHostPort(hostHeader); err == nil && host != "" {
+		return host
+	}
+	return strings.Trim(hostHeader, "[]")
+}
+
+// serviceHostPrefixes are the per-service names published under a mail domain
+// (PLAN.md section 7.3); stripping one yields the mail domain itself.
+var serviceHostPrefixes = []string{"mta-sts.", "autoconfig.", "autodiscover.", "mail."}
+
+func baseDomain(host string) string {
+	for _, prefix := range serviceHostPrefixes {
+		if strings.HasPrefix(host, prefix) {
+			return strings.TrimPrefix(host, prefix)
+		}
+	}
+	return host
 }

services/protocols/internal/presentation/imap/stubs.go

@@ -24,4 +24,3 @@ func (s *session) Unsubscribe(_ string) error                      { return errN
 func (s *session) Append(_ string, _ imap.LiteralReader, _ *imap.AppendOptions) (*imap.AppendData, error) {
 	return nil, errNotYetImplemented
 }
-

services/protocols/internal/presentation/smtp/backend.go

@@ -7,6 +7,7 @@ import (
 	"context"
 	"errors"
 	"io"
+	"net"
 	"strings"
 
 	gosmtp "github.com/emersion/go-smtp"
@@ -24,19 +25,44 @@ func NewBackend(uc *usecase.ProcessInboundEmailUseCase) *Backend {
 	return &Backend{useCase: uc}
 }
 
-func (b *Backend) NewSession(_ *gosmtp.Conn) (gosmtp.Session, error) {
-	return &session{useCase: b.useCase}, nil
+func (b *Backend) NewSession(c *gosmtp.Conn) (gosmtp.Session, error) {
+	return &session{useCase: b.useCase, conn: c}, nil
 }
 
 // session holds one SMTP transaction's accumulated state (RFC 5321 section
 // 4.1.1: MAIL, then one or more RCPT, then DATA, then reset).
 type session struct {
 	useCase            *usecase.ProcessInboundEmailUseCase
+	conn               *gosmtp.Conn
 	from               string
 	recipients         []port.MailboxRecord
 	recipientAddresses []string
 }
 
+// clientIP is the peer address SPF is evaluated against. It returns nil when
+// the connection is not available, which downgrades SPF to "none" rather than
+// producing a wrong verdict.
+func (s *session) clientIP() net.IP {
+	if s.conn == nil || s.conn.Conn() == nil {
+		return nil
+	}
+	if addr, ok := s.conn.Conn().RemoteAddr().(*net.TCPAddr); ok {
+		return addr.IP
+	}
+	host, _, err := net.SplitHostPort(s.conn.Conn().RemoteAddr().String())
+	if err != nil {
+		return nil
+	}
+	return net.ParseIP(host)
+}
+
+func (s *session) heloDomain() string {
+	if s.conn == nil {
+		return ""
+	}
+	return s.conn.Hostname()
+}
+
 func (s *session) Reset() {
 	s.from = ""
 	s.recipients = nil
@@ -107,6 +133,8 @@ func (s *session) Data(r io.Reader) error {
 		Recipients:         s.recipients,
 		RecipientAddresses: s.recipientAddresses,
 		Body:               r,
+		ClientIP:           s.clientIP(),
+		HeloDomain:         s.heloDomain(),
 	})
 	if err != nil {
 		var smtpErr *gosmtp.SMTPError
@@ -114,6 +142,13 @@ func (s *session) Data(r io.Reader) error {
 			return smtpErr
 		}
 		errMsg := err.Error()
+		if strings.HasPrefix(errMsg, "550 ") {
+			return &gosmtp.SMTPError{
+				Code:         550,
+				EnhancedCode: gosmtp.EnhancedCode{5, 7, 1},
+				Message:      strings.TrimPrefix(errMsg, "550 5.7.1 "),
+			}
+		}
 		if strings.HasPrefix(errMsg, "554 ") {
 			return &gosmtp.SMTPError{
 				Code:         554,

services/protocols/internal/presentation/smtp/sasl_login.go

@@ -0,0 +1,67 @@
+package smtppresentation
+
+import (
+	"errors"
+
+	"github.com/emersion/go-sasl"
+)
+
+// loginMechanism is the SASL mechanism name for the legacy LOGIN exchange.
+// PLAN.md section 4 requires it alongside PLAIN because several desktop and
+// mobile clients still offer nothing else. Neither go-sasl nor go-smtp ships a
+// server side for it, so it is implemented here.
+const loginMechanism = "LOGIN"
+
+// LOGIN is not specified by an RFC; it is a de facto mechanism where the
+// server prompts for the username, then for the password, each as a bare
+// challenge string.
+var (
+	loginUsernameChallenge = []byte("Username:")
+	loginPasswordChallenge = []byte("Password:")
+)
+
+// loginAuthenticator verifies a username and password pair.
+type loginAuthenticator func(username, password string) error
+
+// loginServer implements sasl.Server for the LOGIN mechanism.
+type loginServer struct {
+	authenticate loginAuthenticator
+	username     string
+	// state advances from awaiting the username, to awaiting the password,
+	// to finished.
+	state int
+}
+
+const (
+	loginStateAwaitingUsername = iota
+	loginStateAwaitingPassword
+	loginStateDone
+)
+
+func newLoginServer(authenticate loginAuthenticator) sasl.Server {
+	return &loginServer{authenticate: authenticate}
+}
+
+func (s *loginServer) Next(response []byte) (challenge []byte, done bool, err error) {
+	switch s.state {
+	case loginStateAwaitingUsername:
+		// A client may send the username as the initial response, in which
+		// case there is nothing to prompt for yet.
+		if response == nil {
+			return loginUsernameChallenge, false, nil
+		}
+		s.username = string(response)
+		s.state = loginStateAwaitingPassword
+		return loginPasswordChallenge, false, nil
+
+	case loginStateAwaitingPassword:
+		s.state = loginStateDone
+		if err := s.authenticate(s.username, string(response)); err != nil {
+			return nil, false, err
+		}
+		return nil, true, nil
+
+	default:
+		return nil, false, errors.New("sasl: LOGIN exchange already finished")
+	}
+}

services/protocols/internal/presentation/smtp/sasl_login_test.go

@@ -0,0 +1,67 @@
+package smtppresentation
+
+import (
+	"errors"
+	"testing"
+)
+
+// The LOGIN exchange prompts for the username, then the password, and only
+// then authenticates.
+func TestLoginServer_PromptsThenAuthenticates(t *testing.T) {
+	var gotUser, gotPass string
+	server := newLoginServer(func(username, password string) error {
+		gotUser, gotPass = username, password
+		return nil
+	})
+
+	challenge, done, err := server.Next(nil)
+	if err != nil || done || string(challenge) != "Username:" {
+		t.Fatalf("first step: challenge=%q done=%v err=%v", challenge, done, err)
+	}
+
+	challenge, done, err = server.Next([]byte("user@example.test"))
+	if err != nil || done || string(challenge) != "Password:" {
+		t.Fatalf("second step: challenge=%q done=%v err=%v", challenge, done, err)
+	}
+
+	_, done, err = server.Next([]byte("secret"))
+	if err != nil || !done {
+		t.Fatalf("third step: done=%v err=%v", done, err)
+	}
+	if gotUser != "user@example.test" || gotPass != "secret" {
+		t.Errorf("credentials = %q/%q", gotUser, gotPass)
+	}
+}
+
+// A client that sends the username as its initial response skips the first
+// prompt.
+func TestLoginServer_AcceptsInitialResponse(t *testing.T) {
+	server := newLoginServer(func(string, string) error { return nil })
+
+	challenge, done, err := server.Next([]byte("user@example.test"))
+	if err != nil || done || string(challenge) != "Password:" {
+		t.Fatalf("challenge=%q done=%v err=%v", challenge, done, err)
+	}
+}
+
+func TestLoginServer_PropagatesAuthFailure(t *testing.T) {
+	authErr := errors.New("bad credentials")
+	server := newLoginServer(func(string, string) error { return authErr })
+
+	server.Next(nil)
+	server.Next([]byte("user@example.test"))
+	if _, done, err := server.Next([]byte("wrong")); err == nil || done {
+		t.Fatalf("expected the failure to surface: done=%v err=%v", done, err)
+	}
+}
+
+func TestLoginServer_RefusesExtraSteps(t *testing.T) {
+	server := newLoginServer(func(string, string) error { return nil })
+	server.Next(nil)
+	server.Next([]byte("user@example.test"))
+	server.Next([]byte("secret"))
+
+	if _, _, err := server.Next([]byte("extra")); err == nil {
+		t.Fatal("expected an error after the exchange finished")
+	}
+}

services/protocols/internal/presentation/smtp/submission_backend.go

@@ -0,0 +1,159 @@
+package smtppresentation
+
+import (
+	"context"
+	"errors"
+	"io"
+
+	"github.com/emersion/go-sasl"
+	gosmtp "github.com/emersion/go-smtp"
+
+	"lambdamail/protocols/internal/application/port"
+	"lambdamail/protocols/internal/application/usecase"
+)
+
+// SubmissionBackend serves the submission ports (587 and 465). It is a
+// separate backend from the MX one on purpose: submission always requires
+// authentication and always relays outward, while port 25 never authenticates
+// and only accepts mail for local mailboxes (PLAN.md section 4).
+type SubmissionBackend struct {
+	useCase *usecase.ProcessOutboundEmailUseCase
+}
+
+func NewSubmissionBackend(uc *usecase.ProcessOutboundEmailUseCase) *SubmissionBackend {
+	return &SubmissionBackend{useCase: uc}
+}
+
+func (b *SubmissionBackend) NewSession(_ *gosmtp.Conn) (gosmtp.Session, error) {
+	return &submissionSession{useCase: b.useCase}, nil
+}
+
+type submissionSession struct {
+	useCase *usecase.ProcessOutboundEmailUseCase
+	// authenticated is nil until AUTH succeeds; every other command checks it.
+	authenticated *port.MailboxAuth
+	from          string
+	recipients    []string
+}
+
+// AuthMechanisms advertises PLAIN and LOGIN. The server only offers them once
+// the connection is encrypted - go-smtp withholds AUTH before TLS unless
+// AllowInsecureAuth is set, which this deployment never sets (PLAN.md
+// section 4: credentials never travel in the clear).
+func (s *submissionSession) AuthMechanisms() []string {
+	return []string{sasl.Plain, loginMechanism}
+}
+
+func (s *submissionSession) Auth(mech string) (sasl.Server, error) {
+	switch mech {
+	case sasl.Plain:
+		return sasl.NewPlainServer(func(identity, username, password string) error {
+			return s.authenticate(username, password)
+		}), nil
+	case loginMechanism:
+		return newLoginServer(s.authenticate), nil
+	default:
+		return nil, gosmtp.ErrAuthUnsupported
+	}
+}
+
+func (s *submissionSession) authenticate(username, password string) error {
+	rec, err := s.useCase.Authenticate(context.Background(), username, password)
+	if err != nil {
+		return &gosmtp.SMTPError{
+			Code:         535,
+			EnhancedCode: gosmtp.EnhancedCode{5, 7, 8},
+			Message:      "Authentication credentials invalid",
+		}
+	}
+	s.authenticated = rec
+	return nil
+}
+
+func (s *submissionSession) Reset() {
+	s.from = ""
+	s.recipients = nil
+}
+
+func (s *submissionSession) Logout() error {
+	s.authenticated = nil
+	return nil
+}
+
+func (s *submissionSession) Mail(from string, _ *gosmtp.MailOptions) error {
+	if s.authenticated == nil {
+		return errAuthRequired()
+	}
+	if err := usecase.AuthorizeSender(s.authenticated, from); err != nil {
+		return &gosmtp.SMTPError{
+			Code:         550,
+			EnhancedCode: gosmtp.EnhancedCode{5, 7, 1},
+			Message:      "Sender address not owned by the authenticated account",
+		}
+	}
+	s.from = from
+	return nil
+}
+
+func (s *submissionSession) Rcpt(to string, _ *gosmtp.RcptOptions) error {
+	if s.authenticated == nil {
+		return errAuthRequired()
+	}
+	s.recipients = append(s.recipients, to)
+	return nil
+}
+
+func (s *submissionSession) Data(r io.Reader) error {
+	if s.authenticated == nil {
+		return errAuthRequired()
+	}
+	if len(s.recipients) == 0 {
+		return &gosmtp.SMTPError{
+			Code:         503,
+			EnhancedCode: gosmtp.EnhancedCode{5, 5, 1},
+			Message:      "RCPT TO required before DATA",
+		}
+	}
+
+	err := s.useCase.Submit(context.Background(), usecase.ProcessOutboundEmailInput{
+		MailboxID:            s.authenticated.ID,
+		SenderAddr:           s.from,
+		DomainName:           s.authenticated.DomainName,
+		Recipients:           s.recipients,
+		Body:                 r,
+		MaxRecipientsPerHour: s.authenticated.MaxRecipientsPerHour,
+	})
+	if err == nil {
+		return nil
+	}
+
+	// A rate-limited sender gets a 4xx: the message is legitimate, the
+	// account has simply run out of budget for this hour and may retry.
+	if errors.Is(err, usecase.ErrSendLimitExceeded) {
+		return &gosmtp.SMTPError{
+			Code:         451,
+			EnhancedCode: gosmtp.EnhancedCode{4, 7, 0},
+			Message:      "Hourly recipient limit reached, try again later",
+		}
+	}
+
+	return &gosmtp.SMTPError{
+		Code:         451,
+		EnhancedCode: gosmtp.EnhancedCode{4, 3, 0},
+		Message:      "Temporary error accepting message for delivery",
+	}
+}
+
+func errAuthRequired() error {
+	return &gosmtp.SMTPError{
+		Code:         530,
+		EnhancedCode: gosmtp.EnhancedCode{5, 7, 0},
+		Message:      "Authentication required",
+	}
+}
+
+// Ensure the session satisfies both the base and the auth add-on interface.
+var (
+	_ gosmtp.Session     = (*submissionSession)(nil)
+	_ gosmtp.AuthSession = (*submissionSession)(nil)
+)

services/protocols/internal/presentation/smtp/submission_backend_test.go

@@ -0,0 +1,94 @@
+package smtppresentation
+
+import (
+	"strings"
+	"testing"
+
+	gosmtp "github.com/emersion/go-smtp"
+
+	"lambdamail/protocols/internal/application/port"
+	"lambdamail/protocols/internal/application/usecase"
+)
+
+func smtpCode(t *testing.T, err error) int {
+	t.Helper()
+	if err == nil {
+		return 0
+	}
+	var smtpErr *gosmtp.SMTPError
+	if !ok(err, &smtpErr) {
+		t.Fatalf("error is not an SMTPError: %v", err)
+	}
+	return smtpErr.Code
+}
+
+func ok(err error, target **gosmtp.SMTPError) bool {
+	e, is := err.(*gosmtp.SMTPError)
+	if is {
+		*target = e
+	}
+	return is
+}
+
+// Every command before AUTH must be refused: submission that accepted an
+// unauthenticated MAIL FROM would be an open relay.
+func TestSubmissionSession_RefusesCommandsBeforeAuth(t *testing.T) {
+	s := &submissionSession{}
+
+	if got := smtpCode(t, s.Mail("user@example.test", nil)); got != 530 {
+		t.Errorf("MAIL FROM before AUTH = %d, want 530", got)
+	}
+	if got := smtpCode(t, s.Rcpt("rcpt@remote.test", nil)); got != 530 {
+		t.Errorf("RCPT TO before AUTH = %d, want 530", got)
+	}
+	if got := smtpCode(t, s.Data(strings.NewReader("body"))); got != 530 {
+		t.Errorf("DATA before AUTH = %d, want 530", got)
+	}
+}
+
+// An authenticated account must not be able to send as anybody else.
+func TestSubmissionSession_RefusesForeignSender(t *testing.T) {
+	s := &submissionSession{authenticated: &port.MailboxAuth{EmailAddress: "user@example.test"}}
+
+	if err := s.Mail("user@example.test", nil); err != nil {
+		t.Fatalf("sending as itself was refused: %v", err)
+	}
+	if got := smtpCode(t, s.Mail("ceo@example.test", nil)); got != 550 {
+		t.Errorf("MAIL FROM a foreign address = %d, want 550", got)
+	}
+}
+
+func TestSubmissionSession_AdvertisesPlainAndLogin(t *testing.T) {
+	mechs := (&submissionSession{}).AuthMechanisms()
+
+	joined := strings.Join(mechs, " ")
+	if !strings.Contains(joined, "PLAIN") || !strings.Contains(joined, "LOGIN") {
+		t.Errorf("AuthMechanisms = %v, want PLAIN and LOGIN", mechs)
+	}
+}
+
+func TestSubmissionSession_RejectsUnsupportedMechanism(t *testing.T) {
+	if _, err := (&submissionSession{}).Auth("SCRAM-SHA-256"); err == nil {
+		t.Fatal("expected an unsupported-mechanism error")
+	}
+}
+
+// Reset must clear the envelope but keep the session authenticated: RSET
+// starts a new transaction, it does not log the user out.
+func TestSubmissionSession_ResetKeepsAuthentication(t *testing.T) {
+	s := &submissionSession{authenticated: &port.MailboxAuth{EmailAddress: "user@example.test"}}
+	s.Mail("user@example.test", nil)
+	s.Rcpt("rcpt@remote.test", nil)
+
+	s.Reset()
+
+	if s.from != "" || len(s.recipients) != 0 {
+		t.Errorf("envelope survived RSET: from=%q recipients=%v", s.from, s.recipients)
+	}
+	if s.authenticated == nil {
+		t.Error("RSET logged the session out")
+	}
+}
+
+// Compile-time proof that the use case wiring matches what the session needs.
+var _ = usecase.NewProcessOutboundEmailUseCase