diff --git a/docs/MAILBOX-CORE.md b/docs/MAILBOX-CORE.md
new file mode 100644
index 0000000..85acbe9
--- /dev/null
+++ b/docs/MAILBOX-CORE.md
@@ -0,0 +1,57 @@
+# Mailbox core
+
+The webmail, IMAP, POP3 and SMTP are four ways in to one mailbox. They share
+the rules and the data code; none of them has its own copy.
+
+## Where each rule lives
+
+| Rule | One place |
+|------|-----------|
+| Flags, expunge, move, copy, folder delete, counters, quota | `MailStore` (`services/protocols/internal/infrastructure/postgres/mail_store.go`) |
+| Folder and message reads | `mail_store_read.go` (same store) |
+| Credentials (password, app password, scopes) | `usecase/credentials.go` |
+| Sending, and the copy filed in Sent | `ProcessOutboundEmail.Submit` (`FileSentCopy`) |
+| Default folders of a mailbox | SQL function `provision_default_folders` (migration 0014) |
+
+The IMAP repositories, the webmail repository and the TS auth service are thin
+adapters: they translate their protocol and call the code above.
+
+## Invariants
+
+After any operation, through any port:
+
+- `folders.total_count` and `unread_count` equal the live messages and the ones
+  without `\Seen`.
+- `folders.highest_modseq` rises only when a message really changed.
+- `mailboxes.used_bytes` equals the size of the live messages.
+- Deleting twice, or from two ports at once, counts once.
+
+`mail_state_contract_test.go` checks all of this after every operation through
+the IMAP path and the webmail path, and under concurrency.
+`e2e/one_mailbox_everywhere_e2e_test.go` does the same over real SMTP, IMAP and
+HTTP on one mailbox.
+
+## Lock order
+
+Every operation locks **folders first, lowest id first, then the message**
+(`lockFolders`). Two moves in opposite directions, or a move racing a flag
+change, used to deadlock (SQLSTATE 40P01) because they locked in different
+orders. `TestContract_OppositeMovesAndFlagChangesNeverDeadlock` covers it. A new
+operation must follow the same order.
+
+## Adding an operation
+
+1. Put it in `MailStore`, in one transaction, with `lockFolders`.
+2. Make the adapters call it.
+3. Add it to the contract test and run it through both paths.
+
+## Migration 0014
+
+Creates `provision_default_folders`, creates the missing default folders of
+existing mailboxes, and recomputes folder counters and `used_bytes` from the
+messages. It is idempotent and runs with the other migrations at deploy.
+
+## Not done
+
+IMAP `APPEND` is still a stub. When it is implemented, drop a client-appended
+Sent copy that matches the server's one by `Message-ID`.
diff --git a/migrations/0014_mailbox_state_single_source.down.sql b/migrations/0014_mailbox_state_single_source.down.sql
new file mode 100644
index 0000000..9dfb621
--- /dev/null
+++ b/migrations/0014_mailbox_state_single_source.down.sql
@@ -0,0 +1,4 @@
+-- The reconciliation corrected cached numbers and cannot be undone (and has no
+-- reason to be); only the function is removed. Folders it added stay: they are
+-- ordinary folders by now and may hold mail.
+DROP FUNCTION IF EXISTS provision_default_folders(UUID);
diff --git a/migrations/0014_mailbox_state_single_source.up.sql b/migrations/0014_mailbox_state_single_source.up.sql
new file mode 100644
index 0000000..98d52d4
--- /dev/null
+++ b/migrations/0014_mailbox_state_single_source.up.sql
@@ -0,0 +1,77 @@
+-- One definition of "a mailbox's standard folders", and a reconciliation of the
+-- cached numbers that two code paths used to keep on their own.
+--
+-- 1. provision_default_folders
+--
+-- The standard folders were created in two places that had already diverged:
+-- the console's createMailbox added Reports, the CLI that creates the first
+-- administrator did not, so that account had no folder for DMARC and TLS-RPT
+-- reports and they fell into its INBOX. Both now call this function, so the
+-- list lives here and nowhere else. It is idempotent: it adds only what is
+-- missing, matching by name without regard to case.
+CREATE OR REPLACE FUNCTION provision_default_folders(p_mailbox_id UUID)
+RETURNS VOID
+LANGUAGE sql
+AS $$
+    INSERT INTO folders (mailbox_id, name, special_use)
+    SELECT p_mailbox_id, f.name, f.special_use
+      FROM (VALUES ('INBOX',   'inbox'),
+                   ('Sent',    'sent'),
+                   ('Drafts',  'drafts'),
+                   ('Trash',   'trash'),
+                   ('Junk',    'junk'),
+                   ('Archive', 'archive'),
+                   -- Where delivered DMARC and TLS-RPT reports are filed. IMAP has no
+                   -- special-use role for these, so it is matched by name.
+                   ('Reports', NULL)) AS f(name, special_use)
+     WHERE NOT EXISTS (
+            SELECT 1 FROM folders x
+             WHERE x.mailbox_id = p_mailbox_id
+               AND x.parent_id IS NULL
+               AND LOWER(x.name) = LOWER(f.name));
+$$;
+
+-- Mailboxes created before the function that lack a standard folder get it now.
+SELECT provision_default_folders(id) FROM mailboxes;
+
+-- 2. Reconcile the cached numbers with the rows.
+--
+-- Folder counters, and the mailbox's used bytes, are denormalised caches. IMAP
+-- and the webmail each maintained them and each got something wrong (IMAP never
+-- moved the unread counter; the webmail never gave the quota back), so existing
+-- mailboxes carry the drift. Every path now goes through one MailStore that
+-- keeps them true; this corrects what is already stored, once. It only touches
+-- rows that are actually wrong, so it is safe to run again.
+UPDATE folders f
+   SET unread_count = c.unread,
+       total_count  = c.total
+  FROM (
+    SELECT f2.id,
+           COUNT(e.id) FILTER (
+             WHERE NOT EXISTS (
+               SELECT 1 FROM message_flags mf
+                WHERE mf.message_id = e.id
+                  AND mf.received_at = e.received_at
+                  AND mf.flag = '\Seen')
+           )::int AS unread,
+           COUNT(e.id)::int AS total
+      FROM folders f2
+      LEFT JOIN email_messages e
+             ON e.folder_id = f2.id AND e.expunged_at IS NULL
+     GROUP BY f2.id
+  ) AS c
+ WHERE f.id = c.id
+   AND (f.unread_count IS DISTINCT FROM c.unread
+     OR f.total_count  IS DISTINCT FROM c.total);
+
+UPDATE mailboxes m
+   SET used_bytes = COALESCE(s.total, 0)
+  FROM mailboxes m2
+  LEFT JOIN (
+    SELECT mailbox_id, SUM(size_bytes)::bigint AS total
+      FROM email_messages
+     WHERE expunged_at IS NULL
+     GROUP BY mailbox_id
+  ) AS s ON s.mailbox_id = m2.id
+ WHERE m.id = m2.id
+   AND m.used_bytes IS DISTINCT FROM COALESCE(s.total, 0);
diff --git a/services/auth/src/cli.test.ts b/services/auth/src/cli.test.ts
new file mode 100644
index 0000000..f538aa6
--- /dev/null
+++ b/services/auth/src/cli.test.ts
@@ -0,0 +1,46 @@
+import { describe, it, expect, afterAll } from "vitest";
+
+process.env.LAMBDAMAIL_MASTER_KEY ||= "test-master-key-at-least-16-chars";
+process.env.DATABASE_URL = process.env.TEST_DATABASE_URL ?? "";
+
+const hasDatabase = Boolean(process.env.TEST_DATABASE_URL);
+const describeDb = hasDatabase ? describe : describe.skip;
+
+const { createAdmin, CliError } = await import("./cli.js");
+const { query, closePool } = await import("./db.js");
+
+const DOMAIN = `cli-${Date.now()}.test`;
+const EMAIL = `root@${DOMAIN}`;
+
+describeDb("create-admin (command line)", () => {
+  afterAll(async () => {
+    await query(`DELETE FROM domains WHERE name = $1`, [DOMAIN]);
+    await closePool();
+  });
+
+  it("gives the first administrator every standard folder, Reports included", async () => {
+    const log = console.log;
+    console.log = () => undefined;
+    try {
+      await createAdmin(EMAIL, "a-long-enough-password", true);
+    } finally {
+      console.log = log;
+    }
+
+    // This account used to come out without Reports, so its DMARC and TLS-RPT
+    // reports fell into the INBOX: the console and this command each had their
+    // own list of folders and the lists had drifted.
+    const folders = await query<{ name: string; special_use: string | null }>(
+      `SELECT f.name, f.special_use FROM folders f JOIN mailboxes m ON m.id = f.mailbox_id WHERE m.email_address = $1`,
+      [EMAIL],
+    );
+    expect(folders.map((f) => f.name).sort()).toEqual(["Archive", "Drafts", "INBOX", "Junk", "Reports", "Sent", "Trash"]);
+    expect(folders.find((f) => f.name === "Reports")?.special_use).toBeNull();
+    expect(folders.find((f) => f.name === "Sent")?.special_use).toBe("sent");
+  });
+
+  it("refuses with a readable error instead of exiting the process", async () => {
+    await expect(createAdmin(EMAIL, "short", true)).rejects.toBeInstanceOf(CliError);
+    await expect(createAdmin(EMAIL, "a-long-enough-password", true)).rejects.toThrow(/already exists/);
+  });
+});
diff --git a/services/auth/src/cli.ts b/services/auth/src/cli.ts
index 57fce04..7f3351c 100644
--- a/services/auth/src/cli.ts
+++ b/services/auth/src/cli.ts
@@ -13,22 +13,19 @@
  *   node dist/cli.js reset-mfa <email>
  */
 
+import { pathToFileURL } from "node:url";
 import { query, queryOne, closePool } from "./db.js";
 import { hashPassword } from "./crypto.js";
 
 const SYSTEM_ALIASES = ["postmaster", "abuse", "dmarc", "tlsrpt"];
-const STANDARD_FOLDERS: Array<[string, string]> = [
-  ["INBOX", "inbox"],
-  ["Sent", "sent"],
-  ["Drafts", "drafts"],
-  ["Trash", "trash"],
-  ["Junk", "junk"],
-  ["Archive", "archive"],
-];
 
+/** A refusal the operator should read, as opposed to a bug. */
+export class CliError extends Error {}
+
+// Thrown rather than exiting here, so the commands can be exercised from a test;
+// main() prints it as "error: ..." and exits 1, exactly as this used to.
 function fail(message: string): never {
-  console.error(`error: ${message}`);
-  process.exit(1);
+  throw new CliError(message);
 }
 
 function parseAddress(email: string): { localPart: string; domain: string } {
@@ -37,7 +34,7 @@ function parseAddress(email: string): { localPart: string; domain: string } {
   return { localPart: email.slice(0, at).toLowerCase(), domain: email.slice(at + 1).toLowerCase() };
 }
 
-async function createAdmin(email: string, password: string, force: boolean): Promise<void> {
+export async function createAdmin(email: string, password: string, force: boolean): Promise<void> {
   if (password.length < 12) fail("the password must be at least 12 characters");
   const { localPart, domain } = parseAddress(email);
 
@@ -69,13 +66,10 @@ async function createAdmin(email: string, password: string, force: boolean): Pro
   );
 
   // Delivery needs these: a mailbox with no INBOX cannot receive at all, and
-  // one with no Junk used to fail the spam path outright.
-  for (const [name, specialUse] of STANDARD_FOLDERS) {
-    await query(
-      `INSERT INTO folders (mailbox_id, name, special_use) VALUES ($1, $2, $3)`,
-      [mailbox!.id, name, specialUse],
-    );
-  }
+  // one with no Junk used to fail the spam path outright. The list lives in the
+  // database (migration 0014) so the console and this command cannot disagree
+  // about it, as they once did over the Reports folder.
+  await query(`SELECT provision_default_folders($1)`, [mailbox!.id]);
 
   // PLAN.md section 7.4b: the published DNS records name these, and reports
   // bounce if they do not resolve.
@@ -174,10 +168,13 @@ async function main(): Promise<void> {
   }
 }
 
-main()
-  .then(() => closePool())
-  .catch(async (err) => {
-    console.error(`error: ${err instanceof Error ? err.message : String(err)}`);
-    await closePool().catch(() => undefined);
-    process.exit(1);
-  });
+// Only when run as a command, not when a test imports the functions above
+if (process.argv[1] && import.meta.url === pathToFileURL(process.argv[1]).href) {
+  main()
+    .then(() => closePool())
+    .catch(async (err) => {
+      console.error(`error: ${err instanceof Error ? err.message : String(err)}`);
+      await closePool().catch(() => undefined);
+      process.exit(1);
+    });
+}
diff --git a/services/auth/src/repository.ts b/services/auth/src/repository.ts
index 45457a2..0560da4 100644
--- a/services/auth/src/repository.ts
+++ b/services/auth/src/repository.ts
@@ -1004,18 +1004,9 @@ export async function createMailbox(scope: AdminScope, input: CreateMailboxInput
     [input.domainId, localPart, email, hash, input.role, input.quotaBytes],
   );
 
-  await query(
-    `INSERT INTO folders (mailbox_id, name, special_use)
-     SELECT $1, f.name, f.special_use
-       FROM (VALUES ('INBOX','inbox'), ('Sent','sent'), ('Drafts','drafts'),
-                    ('Trash','trash'), ('Junk','junk'), ('Archive','archive'),
-                    -- Where delivered DMARC and TLS-RPT reports are filed.
-                    -- IMAP has no special-use role for these, so it is matched
-                    -- by name. Without the folder the delivery path falls back
-                    -- to INBOX, which is the noise this is here to remove.
-                    ('Reports', NULL)) AS f(name, special_use)`,
-    [created!.id],
-  );
+  // The standard folders come from one definition in the database (migration
+  // 0014), shared with the command that creates the first administrator.
+  await query(`SELECT provision_default_folders($1)`, [created!.id]);
 
   return { status: "OK", id: created!.id, email };
 }
diff --git a/services/protocols/internal/application/usecase/sent_copy_test.go b/services/protocols/internal/application/usecase/sent_copy_test.go
index 019783d..52c5146 100644
--- a/services/protocols/internal/application/usecase/sent_copy_test.go
+++ b/services/protocols/internal/application/usecase/sent_copy_test.go
@@ -137,3 +137,51 @@ func TestSubmit_WorksWithoutASentCopyRepository(t *testing.T) {
 		t.Fatalf("Submit without a Sent repository: %v", err)
 	}
 }
+
+// One rule for every path: a message sent from the webmail and the same message
+// sent by an SMTP client leave the same thing behind in Sent. They used to differ
+// completely - the webmail filed a copy, SMTP filed nothing - because the rule
+// lived in the webmail alone.
+func TestSentCopyIsTheSameWhicheverPathSent(t *testing.T) {
+	mailboxID := uuid.New()
+	messages := &recordingMessageRepository{}
+	submission := NewProcessOutboundEmailUseCase(nil, &countingOutboundRepo{}, &capturingBlobStorage{}, nil)
+	submission.SetSentCopies(messages)
+
+	account := &port.MailboxAuth{ID: mailboxID, EmailAddress: "me@example.test", DomainName: "example.test", MaxRecipientsPerHour: 100}
+	web := &WebmailUseCase{
+		repo:       &stubWebmailRepo{mailboxID: mailboxID.String()},
+		auth:       &stubAuthRepo{account: account},
+		submission: submission,
+		localHost:  "mail.example.test",
+	}
+
+	if err := web.Send(context.Background(), ComposeInput{From: "me@example.test", To: []string{"you@remote.test"}, Subject: "Aviso", Text: "hi"}); err != nil {
+		t.Fatalf("webmail send: %v", err)
+	}
+
+	smtp := ProcessOutboundEmailInput{
+		MailboxID: mailboxID, SenderAddr: "me@example.test", DomainName: "example.test",
+		Recipients: []string{"you@remote.test"}, FileSentCopy: true,
+		Body: bytes.NewBufferString("From: me@example.test\r\nTo: you@remote.test\r\nSubject: Aviso\r\n\r\nhi"),
+	}
+	if err := submission.Submit(context.Background(), smtp); err != nil {
+		t.Fatalf("smtp submit: %v", err)
+	}
+
+	if len(messages.persisted) != 2 {
+		t.Fatalf("want one copy per path (2), got %d: the webmail must not file its own copy as well", len(messages.persisted))
+	}
+	fromWeb, fromSMTP := messages.persisted[0], messages.persisted[1]
+	for _, got := range []port.PersistInboundMessageInput{fromWeb, fromSMTP} {
+		if got.TargetFolderName != "Sent" || !got.AlreadySeen || got.MailboxID != mailboxID {
+			t.Errorf("a Sent copy is not what the rule says: %+v", got)
+		}
+		if got.SenderAddress != "me@example.test" || got.RecipientAddress != "me@example.test" {
+			t.Errorf("a Sent copy belongs to its sender: %+v", got)
+		}
+		if got.Subject != "Aviso" {
+			t.Errorf("subject = %q, want Aviso", got.Subject)
+		}
+	}
+}
diff --git a/services/protocols/internal/application/usecase/webmail_compose_test.go b/services/protocols/internal/application/usecase/webmail_compose_test.go
index 161abf0..0b7dffd 100644
--- a/services/protocols/internal/application/usecase/webmail_compose_test.go
+++ b/services/protocols/internal/application/usecase/webmail_compose_test.go
@@ -197,6 +197,8 @@ func newSendableUseCaseWith(
 	}
 	submission := NewProcessOutboundEmailUseCase(
 		nil, &countingOutboundRepo{}, &capturingBlobStorage{}, &recordingSigner{})
+	// The Sent copy is filed by the submission, as it is for SMTP clients
+	submission.SetSentCopies(messages)
 	return (&WebmailUseCase{
 		repo:       repo,
 		auth:       &stubAuthRepo{account: account},
diff --git a/services/protocols/internal/application/usecase/webmail_mail.go b/services/protocols/internal/application/usecase/webmail_mail.go
index 361c9f2..f67c0af 100644
--- a/services/protocols/internal/application/usecase/webmail_mail.go
+++ b/services/protocols/internal/application/usecase/webmail_mail.go
@@ -32,10 +32,9 @@ type WebmailUseCase struct {
 	submission *ProcessOutboundEmailUseCase
 	auth       port.AuthRepository
 	localHost  string
-	// blobStore and messages file the sender's own copy into Sent, and hold
-	// drafts. Both are optional: when either is nil the copy is skipped rather
-	// than the send failing, because a message that has already been queued
-	// for delivery must not be reported as an error.
+	// blobStore and messages hold drafts. Both are optional: when either is nil
+	// saving a draft reports ErrDraftsUnavailable. (The copy in Sent is filed by
+	// the submission use case, not here.)
 	blobStore port.BlobStorage
 	messages  port.InboundMessageRepository
 }
@@ -53,7 +52,7 @@ func NewWebmailUseCase(
 	return &WebmailUseCase{repo: repo, blobs: blobs, submission: submission, auth: auth, localHost: localHost}
 }
 
-// WithLocalFiling enables the Sent copy and draft storage.
+// WithLocalFiling enables draft storage.
 func (uc *WebmailUseCase) WithLocalFiling(store port.BlobStorage, messages port.InboundMessageRepository) *WebmailUseCase {
 	uc.blobStore = store
 	uc.messages = messages
@@ -188,6 +187,10 @@ func (uc *WebmailUseCase) Send(ctx context.Context, input ComposeInput) error {
 
 	payload := buildMimeMessage(input, recipients, uc.localHost)
 
+	// The copy in Sent is filed by Submit, the same way it is for a client that
+	// sends over SMTP: one rule, one place. It used to be filed here, after the
+	// submission, and not at all for SMTP, so an account that sent by SMTP had an
+	// empty Sent folder.
 	if err := uc.submission.Submit(ctx, ProcessOutboundEmailInput{
 		MailboxID:            account.ID,
 		SenderAddr:           account.EmailAddress,
@@ -195,19 +198,11 @@ func (uc *WebmailUseCase) Send(ctx context.Context, input ComposeInput) error {
 		Recipients:           recipients,
 		Body:                 bytes.NewReader(payload),
 		MaxRecipientsPerHour: account.MaxRecipientsPerHour,
+		FileSentCopy:         true,
 	}); err != nil {
 		return err
 	}
 
-	// Only after the message is durably queued. Filing it first would leave a
-	// copy in Sent for a message that was then rejected by the send limit.
-	//
-	// A failure here is logged and swallowed: the mail is already on its way,
-	// and telling the composer the send failed would invite a duplicate.
-	if err := uc.fileLocalCopy(ctx, account.ID, account.EmailAddress, "Sent", payload); err != nil {
-		log.Printf("webmail: could not file the Sent copy for %s: %v", account.EmailAddress, err)
-	}
-
 	// The draft this message grew out of has been superseded by the real
 	// thing. Swallowed like the Sent copy above and for the same reason: the
 	// mail is already queued, and failing the request now would only invite a
@@ -288,36 +283,6 @@ func (uc *WebmailUseCase) Delete(ctx context.Context, address, folder string, ui
 	}
 }
 
-// fileLocalCopy stores a message the user themselves composed into one of
-// their own folders. It reuses the inbound persistence path so the copy gets a
-// real IMAP UID and shows up over IMAP as well as in the webmail.
-func (uc *WebmailUseCase) fileLocalCopy(
-	ctx context.Context, mailboxID uuid.UUID, address, folder string, payload []byte,
-) error {
-	if uc.blobStore == nil || uc.messages == nil {
-		return nil
-	}
-	blob, err := uc.blobStore.Store(ctx, bytes.NewReader(payload))
-	if err != nil {
-		return err
-	}
-	headers := ExtractMessageHeaders(payload)
-	_, err = uc.messages.PersistAll(ctx, []port.PersistInboundMessageInput{{
-		MailboxID:        mailboxID,
-		Blob:             blob,
-		SenderAddress:    address,
-		RecipientAddress: address,
-		TargetFolderName: folder,
-		Subject:          headers.Subject,
-		Snippet:          headers.Snippet,
-		FromDisplayName:  headers.FromDisplayName,
-		MessageIDHeader:  headers.MessageID,
-		HasAttachments:   headers.HasAttachments,
-		AlreadySeen:      true,
-	}})
-	return err
-}
-
 // SaveDraft files the message being composed into the Drafts folder.
 //
 // Nothing did this before: the composer displayed "draft saved automatically"
diff --git a/services/protocols/internal/e2e/one_mailbox_everywhere_e2e_test.go b/services/protocols/internal/e2e/one_mailbox_everywhere_e2e_test.go
new file mode 100644
index 0000000..3153434
--- /dev/null
+++ b/services/protocols/internal/e2e/one_mailbox_everywhere_e2e_test.go
@@ -0,0 +1,385 @@
+package e2e
+
+import (
+	"bytes"
+	"context"
+	"crypto/tls"
+	"encoding/json"
+	"fmt"
+	"net"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/alexedwards/argon2id"
+	"github.com/emersion/go-imap/v2"
+	"github.com/emersion/go-imap/v2/imapclient"
+	"github.com/emersion/go-imap/v2/imapserver"
+	gosmtp "github.com/emersion/go-smtp"
+	embeddedpostgres "github.com/fergusstrange/embedded-postgres"
+	"github.com/google/uuid"
+
+	"lambdamail/protocols/internal/application/port"
+	appusecase "lambdamail/protocols/internal/application/usecase"
+	"lambdamail/protocols/internal/infrastructure/diskstorage"
+	"lambdamail/protocols/internal/infrastructure/dkim"
+	"lambdamail/protocols/internal/infrastructure/postgres"
+	httppresentation "lambdamail/protocols/internal/presentation/http"
+	imappresentation "lambdamail/protocols/internal/presentation/imap"
+	smtppresentation "lambdamail/protocols/internal/presentation/smtp"
+)
+
+// TestOneMailboxEverywhere is the contract of the whole server: SMTP, IMAP and
+// the webmail are three ways into the same mailbox, so whatever one does, the
+// other two must see, with the same numbers.
+//
+// The webmail used to carry its own copy of the rules and its own queries, and
+// the two stacks drifted apart: mail sent over SMTP never reached Sent, reading
+// over IMAP never moved the unread badge, deleting in the webmail never gave the
+// quota back. This test drives all three on one mailbox, mixing them, and checks
+// after every step that each view agrees with the others and with the data.
+func TestOneMailboxEverywhere(t *testing.T) {
+	if testing.Short() {
+		t.Skip("e2e test skipped in -short mode")
+	}
+	ctx := context.Background()
+
+	pg := embeddedpostgres.NewDatabase(embeddedpostgres.DefaultConfig().
+		Port(15451).
+		RuntimePath(t.TempDir()).
+		StartTimeout(120 * time.Second))
+	if err := pg.Start(); err != nil {
+		t.Fatalf("start embedded postgres: %v", err)
+	}
+	defer pg.Stop()
+
+	pool, err := postgres.NewPool(ctx, "postgres://postgres:postgres@localhost:15451/postgres?sslmode=disable")
+	if err != nil {
+		t.Fatalf("connect pool: %v", err)
+	}
+	defer pool.Close()
+	applyMigrations(t, ctx, pool)
+
+	// ------------------------------------------------------------- fixtures
+	const (
+		address  = "plataforma@everywhere.test"
+		password = "a long enough password"
+	)
+	hash, err := argon2id.CreateHash(password, argon2id.DefaultParams)
+	if err != nil {
+		t.Fatalf("hash: %v", err)
+	}
+	domainID, mailboxID := uuid.New(), uuid.New()
+	pool.Exec(ctx, `INSERT INTO domains (id, name, punycode_name) VALUES ($1, 'everywhere.test', 'everywhere.test')`, domainID)
+	pool.Exec(ctx, `INSERT INTO mailboxes (id, domain_id, local_part, email_address, password_hash) VALUES ($1, $2, 'plataforma', $3, $4)`,
+		mailboxID, domainID, address, hash)
+	// The standard folders come from the one definition in the database
+	if _, err := pool.Exec(ctx, `SELECT provision_default_folders($1)`, mailboxID); err != nil {
+		t.Fatalf("provision folders: %v", err)
+	}
+
+	blobs := diskstorage.NewLocalDiskBlobStorage(pool, t.TempDir())
+	blobReader := diskstorage.NewLocalDiskBlobReader(pool)
+	authRepo := postgres.NewAuthRepository(pool)
+	messages := postgres.NewInboundMessageRepository(pool)
+
+	// Three messages arrive from outside, as the SMTP side would file them
+	inbound := appusecase.NewProcessInboundEmailUseCase(postgres.NewMailboxRepository(pool), blobs, messages)
+	target, err := postgres.NewMailboxRepository(pool).FindActiveByAddress(ctx, address)
+	if err != nil || target == nil {
+		t.Fatalf("resolve mailbox: %v", err)
+	}
+	for i := 1; i <= 3; i++ {
+		raw := fmt.Sprintf("From: alice@remote.test\r\nTo: %s\r\nSubject: inbound %d\r\nMessage-ID: <in%d@remote.test>\r\n\r\nbody %d\r\n", address, i, i, i)
+		if err := inbound.Handle(ctx, appusecase.ProcessInboundEmailInput{
+			Sender: "alice@remote.test", Recipients: []port.MailboxRecord{*target}, RecipientAddresses: []string{address}, Body: strings.NewReader(raw),
+		}); err != nil {
+			t.Fatalf("deliver %d: %v", i, err)
+		}
+	}
+
+	// -------------------------------------------- the three ways in, wired as main.go
+	submissionUC := appusecase.NewProcessOutboundEmailUseCase(authRepo, postgres.NewOutboundRepository(pool), blobs, dkim.NewSigner(nil))
+	submissionUC.SetSentCopies(messages)
+
+	smtpServer := gosmtp.NewServer(smtppresentation.NewSubmissionBackend(submissionUC))
+	smtpServer.Domain = "mail.everywhere.test"
+	smtpServer.TLSConfig = &tls.Config{Certificates: []tls.Certificate{selfSignedTLSCert(t)}}
+	smtpLn, _ := net.Listen("tcp", "127.0.0.1:0")
+	defer smtpLn.Close()
+	go smtpServer.Serve(smtpLn)
+
+	imapUC := appusecase.NewImapSessionUseCase(
+		authRepo, postgres.NewImapFolderRepository(pool), postgres.NewMessageQueryRepository(pool),
+		postgres.NewFlagRepository(pool), blobReader, postgres.NewExpungeRepository(pool), postgres.NewCopyRepository(pool))
+	imapServer := imapserver.New(&imapserver.Options{
+		NewSession: func(c *imapserver.Conn) (imapserver.Session, *imapserver.GreetingData, error) {
+			return imappresentation.NewSession(c, imapUC)
+		},
+		Caps:         imap.CapSet{imap.CapIMAP4rev1: {}, imap.CapMove: {}, imap.CapUIDPlus: {}},
+		InsecureAuth: true,
+	})
+	imapLn, _ := net.Listen("tcp", "127.0.0.1:0")
+	go imapServer.Serve(imapLn)
+	defer imapServer.Close()
+
+	webmailUC := appusecase.NewWebmailUseCase(postgres.NewWebmailRepository(pool), blobReader, submissionUC, authRepo, "mail.everywhere.test").
+		WithLocalFiling(blobs, messages)
+	router := httppresentation.NewRouter(nil, func() error { return nil })
+	router.SetMailAPI(webmailUC, webmailSecret)
+	web := httptest.NewServer(router)
+	defer web.Close()
+	token := mintSession(t, address, "user", time.Hour)
+
+	// --------------------------------------------------------- small drivers
+	webCall := func(method, path string, body any) []byte {
+		t.Helper()
+		var reader *bytes.Reader
+		if body != nil {
+			encoded, _ := json.Marshal(body)
+			reader = bytes.NewReader(encoded)
+		} else {
+			reader = bytes.NewReader(nil)
+		}
+		req, _ := http.NewRequest(method, web.URL+path, reader)
+		req.Header.Set("Cookie", "lm_user_session="+token)
+		req.Header.Set("Content-Type", "application/json")
+		resp, err := http.DefaultClient.Do(req)
+		if err != nil {
+			t.Fatalf("webmail %s %s: %v", method, path, err)
+		}
+		defer resp.Body.Close()
+		buf := new(bytes.Buffer)
+		buf.ReadFrom(resp.Body)
+		if resp.StatusCode >= 300 {
+			t.Fatalf("webmail %s %s = %d: %s", method, path, resp.StatusCode, buf.String())
+		}
+		return buf.Bytes()
+	}
+
+	type webFolder struct {
+		Name        string `json:"name"`
+		UnreadCount int    `json:"unread_count"`
+		TotalCount  int    `json:"total_count"`
+	}
+	webFolders := func() map[string]webFolder {
+		t.Helper()
+		var payload struct {
+			Folders []webFolder `json:"folders"`
+		}
+		raw := webCall(http.MethodGet, "/api/v1/mail/folders", nil)
+		if err := json.Unmarshal(raw, &payload); err != nil || payload.Folders == nil {
+			var plain []webFolder
+			if err2 := json.Unmarshal(raw, &plain); err2 != nil {
+				t.Fatalf("decode folders: %v / %v: %s", err, err2, raw)
+			}
+			payload.Folders = plain
+		}
+		out := map[string]webFolder{}
+		for _, f := range payload.Folders {
+			out[f.Name] = f
+		}
+		return out
+	}
+	type webMessage struct {
+		UID     uint32 `json:"uid"`
+		Subject string `json:"subject"`
+		Seen    bool   `json:"seen"`
+	}
+	webMessages := func(folder string) []webMessage {
+		t.Helper()
+		var payload struct {
+			Messages []webMessage `json:"messages"`
+		}
+		raw := webCall(http.MethodGet, "/api/v1/mail/messages?folder="+folder, nil)
+		if err := json.Unmarshal(raw, &payload); err != nil || payload.Messages == nil {
+			var plain []webMessage
+			if err2 := json.Unmarshal(raw, &plain); err2 != nil {
+				t.Fatalf("decode messages: %v / %v: %s", err, err2, raw)
+			}
+			payload.Messages = plain
+		}
+		return payload.Messages
+	}
+
+	imapClient, err := imapclient.DialInsecure(imapLn.Addr().String(), nil)
+	if err != nil {
+		t.Fatalf("dial imap: %v", err)
+	}
+	defer imapClient.Close()
+	if err := imapClient.Login(address, password).Wait(); err != nil {
+		t.Fatalf("imap login: %v", err)
+	}
+	imapExists := func(folder string) int {
+		t.Helper()
+		data, err := imapClient.Select(folder, nil).Wait()
+		if err != nil {
+			t.Fatalf("imap select %s: %v", folder, err)
+		}
+		return int(data.NumMessages)
+	}
+	imapFlags := func(folder string) map[uint32][]imap.Flag {
+		t.Helper()
+		imapExists(folder)
+		all := imap.UIDSet{}
+		all.AddRange(1, 0) // 1:*
+		cmd := imapClient.Fetch(all, &imap.FetchOptions{UID: true, Flags: true})
+		out := map[uint32][]imap.Flag{}
+		msgs, err := cmd.Collect()
+		if err != nil {
+			t.Fatalf("imap fetch flags in %s: %v", folder, err)
+		}
+		for _, m := range msgs {
+			out[uint32(m.UID)] = m.Flags
+		}
+		return out
+	}
+
+	// agree compares what the webmail and IMAP each say about every folder, and
+	// both with the rows: the one thing that must never differ
+	agree := func(after string) {
+		t.Helper()
+		assertEverywhere := webFolders()
+		for _, name := range []string{"INBOX", "Sent", "Trash", "Drafts"} {
+			if got, want := imapExists(name), assertEverywhere[name].TotalCount; got != want {
+				t.Errorf("after %s: %s holds %d messages over IMAP and %d in the webmail", after, name, got, want)
+			}
+		}
+		var badFolders, badBytes int
+		pool.QueryRow(ctx, `
+			SELECT COUNT(*) FROM (
+			  SELECT f.id FROM folders f
+			    LEFT JOIN email_messages e ON e.folder_id = f.id AND e.expunged_at IS NULL
+			   WHERE f.mailbox_id = $1
+			   GROUP BY f.id, f.total_count, f.unread_count
+			  HAVING f.total_count <> COUNT(e.id)
+			      OR f.unread_count <> COUNT(e.id) FILTER (WHERE NOT EXISTS (
+			           SELECT 1 FROM message_flags mf WHERE mf.message_id = e.id AND mf.received_at = e.received_at AND mf.flag = '\Seen'))
+			) x`, mailboxID).Scan(&badFolders)
+		pool.QueryRow(ctx, `
+			SELECT COUNT(*) FROM mailboxes m
+			 WHERE m.id = $1 AND m.used_bytes <> COALESCE((SELECT SUM(size_bytes) FROM email_messages WHERE mailbox_id = m.id AND expunged_at IS NULL), 0)`,
+			mailboxID).Scan(&badBytes)
+		if badFolders != 0 {
+			t.Errorf("after %s: %d folder(s) have cached counters that differ from their messages", after, badFolders)
+		}
+		if badBytes != 0 {
+			t.Errorf("after %s: the quota differs from the bytes actually stored", after)
+		}
+	}
+
+	agree("delivery")
+	if f := webFolders(); f["INBOX"].UnreadCount != 3 || f["INBOX"].TotalCount != 3 {
+		t.Fatalf("INBOX should start with 3 unread of 3, the webmail says %+v", f["INBOX"])
+	}
+
+	// ----- 1. SMTP sends a message; Sent must show it in the webmail and over IMAP
+	smtpClient, err := gosmtp.DialStartTLS(smtpLn.Addr().String(), &tls.Config{InsecureSkipVerify: true})
+	if err != nil {
+		t.Fatalf("dial smtp: %v", err)
+	}
+	if err := smtpClient.Auth(plainAuth(address, password)); err != nil {
+		t.Fatalf("smtp auth: %v", err)
+	}
+	smtpClient.Mail(address, nil)
+	smtpClient.Rcpt("bob@remote.test", nil)
+	w, _ := smtpClient.Data()
+	w.Write([]byte("From: " + address + "\r\nTo: bob@remote.test\r\nSubject: sent over smtp\r\nMessage-ID: <smtp1@everywhere.test>\r\n\r\nhello\r\n"))
+	if err := w.Close(); err != nil {
+		t.Fatalf("smtp data: %v", err)
+	}
+	smtpClient.Quit()
+
+	agree("sending over SMTP")
+	if sent := webMessages("sent"); len(sent) != 1 || sent[0].Subject != "sent over smtp" {
+		t.Fatalf("the webmail's Sent should hold the SMTP message, got %+v", sent)
+	}
+	if n := imapExists("Sent"); n != 1 {
+		t.Fatalf("IMAP's Sent holds %d messages after an SMTP send, want 1", n)
+	}
+	if f := webFolders(); f["Sent"].UnreadCount != 0 {
+		t.Errorf("the sender's own copy shows as unread: %+v", f["Sent"])
+	}
+
+	// ----- 2. the webmail sends one too: it must land in the same place, once
+	webCall(http.MethodPost, "/api/v1/mail/send", map[string]any{"to": []string{"carol@remote.test"}, "subject": "sent from webmail", "text": "hi"})
+	agree("sending from the webmail")
+	if n := imapExists("Sent"); n != 2 {
+		t.Fatalf("Sent holds %d messages after one SMTP send and one webmail send, want exactly 2", n)
+	}
+
+	// ----- 3. read in the webmail; IMAP must see \Seen and the badge must fall
+	inbox := webMessages("inbox")
+	if len(inbox) != 3 {
+		t.Fatalf("webmail lists %d INBOX messages, want 3", len(inbox))
+	}
+	uidA, uidB, uidC := inbox[2].UID, inbox[1].UID, inbox[0].UID // oldest first by UID
+	webCall(http.MethodPost, "/api/v1/mail/seen", map[string]any{"folder": "inbox", "uid": uidA, "seen": true})
+	agree("reading a message in the webmail")
+	if flags := imapFlags("INBOX")[uidA]; !hasFlag(flags, imap.FlagSeen) {
+		t.Errorf("IMAP does not see the message the webmail marked as read: %v", flags)
+	}
+	if f := webFolders(); f["INBOX"].UnreadCount != 2 {
+		t.Errorf("INBOX unread = %d after one read, want 2", f["INBOX"].UnreadCount)
+	}
+
+	// ----- 4. read over IMAP; the webmail's badge must follow (it never did)
+	imapExists("INBOX")
+	if err := imapClient.Store(imap.UIDSetNum(imap.UID(uidB)), &imap.StoreFlags{Op: imap.StoreFlagsAdd, Silent: true, Flags: []imap.Flag{imap.FlagSeen}}, nil).Close(); err != nil {
+		t.Fatalf("imap store: %v", err)
+	}
+	agree("reading a message over IMAP")
+	if f := webFolders(); f["INBOX"].UnreadCount != 1 {
+		t.Errorf("INBOX unread = %d after a read over IMAP, want 1: the badge ignored it", f["INBOX"].UnreadCount)
+	}
+	for _, m := range webMessages("inbox") {
+		if m.UID == uidB && !m.Seen {
+			t.Error("the webmail lists the message IMAP marked as read as unread")
+		}
+	}
+
+	// ----- 5. delete over IMAP (\Deleted + EXPUNGE); the webmail list shrinks, the quota is returned
+	imapExists("INBOX")
+	if err := imapClient.Store(imap.UIDSetNum(imap.UID(uidC)), &imap.StoreFlags{Op: imap.StoreFlagsAdd, Silent: true, Flags: []imap.Flag{imap.FlagDeleted}}, nil).Close(); err != nil {
+		t.Fatalf("imap store deleted: %v", err)
+	}
+	if err := imapClient.Expunge().Close(); err != nil {
+		t.Fatalf("imap expunge: %v", err)
+	}
+	agree("deleting over IMAP")
+	if n := len(webMessages("inbox")); n != 2 {
+		t.Errorf("the webmail lists %d INBOX messages after an IMAP delete, want 2", n)
+	}
+
+	// ----- 6. delete in the webmail (to Trash); IMAP sees it in Trash and not in INBOX
+	webCall(http.MethodPost, "/api/v1/mail/delete", map[string]any{"folder": "inbox", "uid": uidA})
+	agree("deleting in the webmail")
+	if n := imapExists("Trash"); n != 1 {
+		t.Errorf("IMAP's Trash holds %d messages, want 1", n)
+	}
+	if n := imapExists("INBOX"); n != 1 {
+		t.Errorf("IMAP's INBOX holds %d messages, want 1", n)
+	}
+
+	// ----- 7. empty the Trash in the webmail: the bytes go back to the quota
+	trash := webMessages("trash")
+	if len(trash) != 1 {
+		t.Fatalf("the webmail lists %d Trash messages, want 1", len(trash))
+	}
+	webCall(http.MethodPost, "/api/v1/mail/delete", map[string]any{"folder": "trash", "uid": trash[0].UID})
+	agree("emptying the Trash")
+	if n := imapExists("Trash"); n != 0 {
+		t.Errorf("IMAP's Trash holds %d messages after emptying it, want 0", n)
+	}
+}
+
+func hasFlag(flags []imap.Flag, want imap.Flag) bool {
+	for _, f := range flags {
+		if f == want {
+			return true
+		}
+	}
+	return false
+}
diff --git a/services/protocols/internal/infrastructure/postgres/copy_repository.go b/services/protocols/internal/infrastructure/postgres/copy_repository.go
index 7c6482d..b98dfb3 100644
--- a/services/protocols/internal/infrastructure/postgres/copy_repository.go
+++ b/services/protocols/internal/infrastructure/postgres/copy_repository.go
@@ -2,133 +2,21 @@ package postgres
 
 import (
 	"context"
-	"fmt"
 
-	"github.com/google/uuid"
 	"github.com/jackc/pgx/v5/pgxpool"
 
 	"lambdamail/protocols/internal/application/port"
 )
 
-// CopyRepository implements port.CopyRepository against Postgres. One
-// transaction per copied message, mirroring InboundMessageRepository's
-// established per-message transactional pattern (PLAN.md section 6.1).
+// CopyRepository implements port.CopyRepository (IMAP COPY) over MailStore.
 type CopyRepository struct {
-	pool *pgxpool.Pool
+	store *MailStore
 }
 
 func NewCopyRepository(pool *pgxpool.Pool) *CopyRepository {
-	return &CopyRepository{pool: pool}
+	return &CopyRepository{store: NewMailStore(pool)}
 }
 
 func (r *CopyRepository) CopyMessages(ctx context.Context, sourceFolderID string, uids []uint32, destFolderID string) ([]port.CopiedMessage, error) {
-	results := make([]port.CopiedMessage, 0, len(uids))
-	for _, uid := range uids {
-		destUID, err := r.copyOne(ctx, sourceFolderID, uid, destFolderID)
-		if err != nil {
-			return nil, fmt.Errorf("copy uid %d: %w", uid, err)
-		}
-		results = append(results, port.CopiedMessage{SourceUID: uid, DestUID: destUID})
-	}
-	return results, nil
-}
-
-func (r *CopyRepository) copyOne(ctx context.Context, sourceFolderID string, sourceUID uint32, destFolderID string) (uint32, error) {
-	tx, err := r.pool.Begin(ctx)
-	if err != nil {
-		return 0, fmt.Errorf("begin transaction: %w", err)
-	}
-	defer tx.Rollback(ctx)
-
-	var sourceMessageID string
-	var blobID, senderAddress string
-	var recipientAddresses []string
-	var sizeBytes int64
-	var spfResult, dkimResult, dmarcResult *string
-	var fromDisplayName, subject, snippet, messageIDHeader, inReplyTo *string
-	var threadID *uuid.UUID
-	var hasAttachments bool
-	var arcResult, daneStatus, tlsVersion, spamVerdict, virusName *string
-	var spamScore float64
-	err = tx.QueryRow(ctx, `
-		SELECT id, blob_id, sender_address, recipient_addresses, size_bytes, spf_result, dkim_result, dmarc_result,
-			from_display_name, subject, snippet, message_id_header, in_reply_to, thread_id, has_attachments,
-			arc_result, dane_status, tls_version, spam_score, spam_verdict, virus_name
-		FROM email_messages WHERE folder_id = $1 AND uid = $2 AND expunged_at IS NULL
-	`, sourceFolderID, sourceUID).Scan(&sourceMessageID, &blobID, &senderAddress, &recipientAddresses, &sizeBytes, &spfResult, &dkimResult, &dmarcResult,
-		&fromDisplayName, &subject, &snippet, &messageIDHeader, &inReplyTo, &threadID, &hasAttachments,
-		&arcResult, &daneStatus, &tlsVersion, &spamScore, &spamVerdict, &virusName)
-	if err != nil {
-		return 0, fmt.Errorf("find source message: %w", err)
-	}
-
-	// uid_next is BIGINT; the destination UID we allocate for this message
-	// is the folder's current uid_next value before advancing it.
-	var destUIDNext int64
-	if err := tx.QueryRow(ctx, `
-		SELECT uid_next FROM folders WHERE id = $1 FOR UPDATE
-	`, destFolderID).Scan(&destUIDNext); err != nil {
-		return 0, fmt.Errorf("lock destination folder: %w", err)
-	}
-	destUID := uint32(destUIDNext)
-
-	var destModSeq int64
-	if err := tx.QueryRow(ctx, `UPDATE folders SET uid_next = uid_next + 1, highest_modseq = highest_modseq + 1, total_count = total_count + 1 WHERE id = $1 RETURNING highest_modseq`, destFolderID).Scan(&destModSeq); err != nil {
-		return 0, fmt.Errorf("advance destination uid_next and highest_modseq: %w", err)
-	}
-
-	var wasSeen bool
-	if err := tx.QueryRow(ctx, `
-		SELECT EXISTS (SELECT 1 FROM message_flags WHERE message_id = $1 AND flag = '\Seen')
-	`, sourceMessageID).Scan(&wasSeen); err != nil {
-		return 0, fmt.Errorf("check source seen flag: %w", err)
-	}
-	if !wasSeen {
-		if _, err := tx.Exec(ctx, `UPDATE folders SET unread_count = unread_count + 1 WHERE id = $1`, destFolderID); err != nil {
-			return 0, fmt.Errorf("increment destination unread_count: %w", err)
-		}
-	}
-
-	var destMailboxID string
-	if err := tx.QueryRow(ctx, `SELECT mailbox_id FROM folders WHERE id = $1`, destFolderID).Scan(&destMailboxID); err != nil {
-		return 0, fmt.Errorf("find destination mailbox: %w", err)
-	}
-
-	var destMessageID string
-	var destReceivedAt any
-	err = tx.QueryRow(ctx, `
-		INSERT INTO email_messages (
-			mailbox_id, folder_id, uid, modseq, blob_id,
-			sender_address, recipient_addresses, size_bytes,
-			spf_result, dkim_result, dmarc_result,
-			from_display_name, subject, snippet, message_id_header, in_reply_to, thread_id, has_attachments,
-			arc_result, dane_status, tls_version, spam_score, spam_verdict, virus_name
-		) VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14, $15, $16, $17, $18, $19, $20, $21, $22, $23, $24)
-		RETURNING id, received_at
-	`, destMailboxID, destFolderID, destUID, destModSeq, blobID, senderAddress, recipientAddresses, sizeBytes, spfResult, dkimResult, dmarcResult,
-		fromDisplayName, subject, snippet, messageIDHeader, inReplyTo, threadID, hasAttachments,
-		arcResult, daneStatus, tlsVersion, spamScore, spamVerdict, virusName).Scan(&destMessageID, &destReceivedAt)
-	if err != nil {
-		return 0, fmt.Errorf("insert copied message: %w", err)
-	}
-
-	if _, err := tx.Exec(ctx, `UPDATE message_blobs SET ref_count = ref_count + 1 WHERE id = $1`, blobID); err != nil {
-		return 0, fmt.Errorf("increment blob ref_count: %w", err)
-	}
-
-	if _, err := tx.Exec(ctx, `UPDATE mailboxes SET used_bytes = used_bytes + $1 WHERE id = $2`, sizeBytes, destMailboxID); err != nil {
-		return 0, fmt.Errorf("increment destination mailbox used_bytes: %w", err)
-	}
-
-	if _, err := tx.Exec(ctx, `
-		INSERT INTO message_flags (message_id, received_at, flag)
-		SELECT $1, $2, flag FROM message_flags WHERE message_id = $3
-	`, destMessageID, destReceivedAt, sourceMessageID); err != nil {
-		return 0, fmt.Errorf("copy flags: %w", err)
-	}
-
-	if err := tx.Commit(ctx); err != nil {
-		return 0, fmt.Errorf("commit: %w", err)
-	}
-	return destUID, nil
+	return r.store.Copy(ctx, sourceFolderID, uids, destFolderID)
 }
diff --git a/services/protocols/internal/infrastructure/postgres/expunge_repository.go b/services/protocols/internal/infrastructure/postgres/expunge_repository.go
index 865c207..45a56f4 100644
--- a/services/protocols/internal/infrastructure/postgres/expunge_repository.go
+++ b/services/protocols/internal/infrastructure/postgres/expunge_repository.go
@@ -2,91 +2,21 @@ package postgres
 
 import (
 	"context"
-	"fmt"
 
 	"github.com/jackc/pgx/v5/pgxpool"
 )
 
-// ExpungeRepository implements port.ExpungeRepository against Postgres.
+// ExpungeRepository implements port.ExpungeRepository (IMAP EXPUNGE). MailStore
+// does the work - counters, modseq and the quota all move there, for every path.
 type ExpungeRepository struct {
-	pool *pgxpool.Pool
+	store *MailStore
 }
 
 func NewExpungeRepository(pool *pgxpool.Pool) *ExpungeRepository {
-	return &ExpungeRepository{pool: pool}
+	return &ExpungeRepository{store: NewMailStore(pool)}
 }
 
-// Expunge marks each message identified by (folderID, uid) in uids as
-// expunged, decrements the folder's total_count (and unread_count for any
-// message that lacked \Seen), and decrements the owning mailbox's
-// used_bytes by the message's size_bytes. used_bytes is logical,
-// message-level accounting (mirroring how delivery and COPY add to it per
-// message even when the underlying blob is deduplicated), so it is
-// decremented here independently of message_blobs.ref_count, whose
-// reclamation is deferred to a future GC task. One transaction per call;
-// each uid is processed sequentially within it.
 func (r *ExpungeRepository) Expunge(ctx context.Context, folderID string, uids []uint32) error {
-	if len(uids) == 0 {
-		return nil
-	}
-	tx, err := r.pool.Begin(ctx)
-	if err != nil {
-		return fmt.Errorf("begin transaction: %w", err)
-	}
-	defer tx.Rollback(ctx)
-
-	for _, uid := range uids {
-		var wasSeen bool
-		var mailboxID string
-		var sizeBytes int64
-		err := tx.QueryRow(ctx, `
-			SELECT EXISTS (
-				SELECT 1 FROM message_flags mf
-				JOIN email_messages m ON m.id = mf.message_id AND m.received_at = mf.received_at
-				WHERE m.folder_id = $1 AND m.uid = $2 AND mf.flag = '\Seen'
-			), m.mailbox_id, m.size_bytes
-			FROM email_messages m
-			WHERE m.folder_id = $1 AND m.uid = $2
-		`, folderID, uid).Scan(&wasSeen, &mailboxID, &sizeBytes)
-		if err != nil {
-			return fmt.Errorf("check seen flag for uid %d: %w", uid, err)
-		}
-
-		tag, err := tx.Exec(ctx, `
-			UPDATE email_messages SET expunged_at = NOW()
-			WHERE folder_id = $1 AND uid = $2 AND expunged_at IS NULL
-		`, folderID, uid)
-		if err != nil {
-			return fmt.Errorf("expunge uid %d: %w", uid, err)
-		}
-		if tag.RowsAffected() == 0 {
-			// Nothing to expunge (already expunged or never existed) - the
-			// caller already verified \Deleted, so don't touch counters for
-			// a message that wasn't actually there.
-			continue
-		}
-
-		unreadDelta := 0
-		if !wasSeen {
-			unreadDelta = 1
-		}
-		if _, err := tx.Exec(ctx, `
-			UPDATE folders SET total_count = total_count - 1, unread_count = unread_count - $1, highest_modseq = highest_modseq + 1
-			WHERE id = $2
-		`, unreadDelta, folderID); err != nil {
-			return fmt.Errorf("decrement folder counters for uid %d: %w", uid, err)
-		}
-
-		if _, err := tx.Exec(ctx, `
-			UPDATE mailboxes SET used_bytes = used_bytes - $1
-			WHERE id = $2
-		`, sizeBytes, mailboxID); err != nil {
-			return fmt.Errorf("decrement mailbox used_bytes for uid %d: %w", uid, err)
-		}
-	}
-
-	if err := tx.Commit(ctx); err != nil {
-		return fmt.Errorf("commit: %w", err)
-	}
-	return nil
+	_, err := r.store.Expunge(ctx, folderID, uids)
+	return err
 }
diff --git a/services/protocols/internal/infrastructure/postgres/flag_repository.go b/services/protocols/internal/infrastructure/postgres/flag_repository.go
index cedb2c1..eecd3ac 100644
--- a/services/protocols/internal/infrastructure/postgres/flag_repository.go
+++ b/services/protocols/internal/infrastructure/postgres/flag_repository.go
@@ -2,95 +2,23 @@ package postgres
 
 import (
 	"context"
-	"fmt"
 
 	"github.com/jackc/pgx/v5/pgxpool"
 
 	"lambdamail/protocols/internal/application/port"
 )
 
-// FlagRepository implements port.FlagRepository against Postgres.
+// FlagRepository implements port.FlagRepository (IMAP STORE). The work is done
+// by MailStore, which every path shares; this only names the message the way
+// IMAP does, by folder and UID.
 type FlagRepository struct {
-	pool *pgxpool.Pool
+	store *MailStore
 }
 
 func NewFlagRepository(pool *pgxpool.Pool) *FlagRepository {
-	return &FlagRepository{pool: pool}
+	return &FlagRepository{store: NewMailStore(pool)}
 }
 
 func (r *FlagRepository) SetFlags(ctx context.Context, folderID string, uid uint32, op port.FlagOp, flags []string, unchangedSince uint64) (bool, error) {
-	tx, err := r.pool.Begin(ctx)
-	if err != nil {
-		return false, fmt.Errorf("begin transaction: %w", err)
-	}
-	defer tx.Rollback(ctx)
-
-	var currentModSeq uint64
-	if err := tx.QueryRow(ctx, `
-		SELECT modseq FROM email_messages WHERE folder_id = $1 AND uid = $2 AND expunged_at IS NULL
-	`, folderID, uid).Scan(&currentModSeq); err != nil {
-		return false, fmt.Errorf("find message folder=%s uid=%d: %w", folderID, uid, err)
-	}
-
-	if unchangedSince > 0 && currentModSeq > unchangedSince {
-		return false, nil
-	}
-
-	var newModSeq uint64
-	if err := tx.QueryRow(ctx, `
-		UPDATE folders SET highest_modseq = highest_modseq + 1 WHERE id = $1 RETURNING highest_modseq
-	`, folderID).Scan(&newModSeq); err != nil {
-		return false, fmt.Errorf("advance highest_modseq for folder %s: %w", folderID, err)
-	}
-
-	if _, err := tx.Exec(ctx, `
-		UPDATE email_messages SET modseq = $1 WHERE folder_id = $2 AND uid = $3 AND expunged_at IS NULL
-	`, newModSeq, folderID, uid); err != nil {
-		return false, fmt.Errorf("update message modseq: %w", err)
-	}
-
-	switch op {
-	case port.FlagOpAdd:
-		for _, flag := range flags {
-			if _, err := tx.Exec(ctx, `
-				INSERT INTO message_flags (message_id, received_at, flag)
-				SELECT id, received_at, $3 FROM email_messages WHERE folder_id = $1 AND uid = $2 AND expunged_at IS NULL
-				ON CONFLICT DO NOTHING
-			`, folderID, uid, flag); err != nil {
-				return false, fmt.Errorf("add flag %q: %w", flag, err)
-			}
-		}
-	case port.FlagOpDel:
-		for _, flag := range flags {
-			if _, err := tx.Exec(ctx, `
-				DELETE FROM message_flags WHERE (message_id, received_at) IN (
-					SELECT id, received_at FROM email_messages WHERE folder_id = $1 AND uid = $2 AND expunged_at IS NULL
-				) AND flag = $3
-			`, folderID, uid, flag); err != nil {
-				return false, fmt.Errorf("delete flag %q: %w", flag, err)
-			}
-		}
-	case port.FlagOpSet:
-		if _, err := tx.Exec(ctx, `
-			DELETE FROM message_flags WHERE (message_id, received_at) IN (
-				SELECT id, received_at FROM email_messages WHERE folder_id = $1 AND uid = $2 AND expunged_at IS NULL
-			)
-		`, folderID, uid); err != nil {
-			return false, fmt.Errorf("clear flags before set: %w", err)
-		}
-		for _, flag := range flags {
-			if _, err := tx.Exec(ctx, `
-				INSERT INTO message_flags (message_id, received_at, flag)
-				SELECT id, received_at, $3 FROM email_messages WHERE folder_id = $1 AND uid = $2 AND expunged_at IS NULL
-				ON CONFLICT DO NOTHING
-			`, folderID, uid, flag); err != nil {
-				return false, fmt.Errorf("set flag %q: %w", flag, err)
-			}
-		}
-	}
-
-	if err := tx.Commit(ctx); err != nil {
-		return false, fmt.Errorf("commit: %w", err)
-	}
-	return true, nil
+	return r.store.SetFlags(ctx, folderID, uid, op, flags, unchangedSince)
 }
diff --git a/services/protocols/internal/infrastructure/postgres/imap_folder_repository.go b/services/protocols/internal/infrastructure/postgres/imap_folder_repository.go
index ee8a6b9..12ecd3a 100644
--- a/services/protocols/internal/infrastructure/postgres/imap_folder_repository.go
+++ b/services/protocols/internal/infrastructure/postgres/imap_folder_repository.go
@@ -3,57 +3,50 @@ package postgres
 import (
 	"context"
 
-	"github.com/jackc/pgx/v5"
 	"github.com/jackc/pgx/v5/pgxpool"
 
 	"lambdamail/protocols/internal/application/port"
 )
 
-// ImapFolderRepository implements port.ImapFolderRepository against Postgres.
+// ImapFolderRepository resolves a mailbox's folders for LIST and SELECT. The
+// question is answered by MailStore, the same one the webmail asks, so a folder
+// reports the same number of messages on both.
 type ImapFolderRepository struct {
-	pool *pgxpool.Pool
+	store *MailStore
 }
 
 func NewImapFolderRepository(pool *pgxpool.Pool) *ImapFolderRepository {
-	return &ImapFolderRepository{pool: pool}
+	return &ImapFolderRepository{store: NewMailStore(pool)}
+}
+
+func imapRecord(f FolderInfo) port.ImapFolderRecord {
+	return port.ImapFolderRecord{
+		ID:            f.ID,
+		Name:          f.Name,
+		UIDNext:       uint32(f.UIDNext),
+		UIDValidity:   uint32(f.UIDValidity),
+		NumMessages:   uint32(f.Total),
+		HighestModSeq: uint64(f.HighestModSeq),
+	}
 }
 
 func (r *ImapFolderRepository) FindByName(ctx context.Context, mailboxID, name string) (*port.ImapFolderRecord, error) {
-	row := r.pool.QueryRow(ctx, `
-		SELECT f.id, f.name, f.uid_next, f.uid_validity, f.total_count, f.highest_modseq
-		FROM folders f
-		WHERE f.mailbox_id = $1 AND f.name = $2
-	`, mailboxID, name)
-
-	var rec port.ImapFolderRecord
-	if err := row.Scan(&rec.ID, &rec.Name, &rec.UIDNext, &rec.UIDValidity, &rec.NumMessages, &rec.HighestModSeq); err != nil {
-		if err == pgx.ErrNoRows {
-			return nil, nil
-		}
+	f, err := r.store.FolderByName(ctx, mailboxID, name)
+	if err != nil || f == nil {
 		return nil, err
 	}
+	rec := imapRecord(*f)
 	return &rec, nil
 }
 
 func (r *ImapFolderRepository) ListFolders(ctx context.Context, mailboxID string) ([]port.ImapFolderRecord, error) {
-	rows, err := r.pool.Query(ctx, `
-		SELECT f.id, f.name, f.uid_next, f.uid_validity, f.total_count, f.highest_modseq
-		FROM folders f
-		WHERE f.mailbox_id = $1
-		ORDER BY f.name
-	`, mailboxID)
+	folders, err := r.store.Folders(ctx, mailboxID)
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
-
 	var out []port.ImapFolderRecord
-	for rows.Next() {
-		var rec port.ImapFolderRecord
-		if err := rows.Scan(&rec.ID, &rec.Name, &rec.UIDNext, &rec.UIDValidity, &rec.NumMessages, &rec.HighestModSeq); err != nil {
-			return nil, err
-		}
-		out = append(out, rec)
+	for _, f := range folders {
+		out = append(out, imapRecord(f))
 	}
-	return out, rows.Err()
+	return out, nil
 }
diff --git a/services/protocols/internal/infrastructure/postgres/mail_state_contract_test.go b/services/protocols/internal/infrastructure/postgres/mail_state_contract_test.go
new file mode 100644
index 0000000..54f041c
--- /dev/null
+++ b/services/protocols/internal/infrastructure/postgres/mail_state_contract_test.go
@@ -0,0 +1,534 @@
+package postgres
+
+import (
+	"context"
+	"fmt"
+	"testing"
+
+	"github.com/google/uuid"
+	"github.com/jackc/pgx/v5/pgxpool"
+
+	"lambdamail/protocols/internal/application/port"
+)
+
+// The mailbox state contract.
+//
+// A message can be read, flagged, moved, copied and deleted from IMAP, from the
+// webmail, and by the server itself. All of them change the same rows, and the
+// rows carry cached numbers (folder counters, the folder's modseq, the
+// mailbox's used bytes) that every path must keep true. Before there was one
+// implementation, each path kept them true on its own, and they drifted:
+//
+//   - reading a message over IMAP never moved the unread counter, so the badge
+//     in the webmail and IMAP STATUS disagreed with the flags;
+//   - deleting from the webmail never gave the quota back;
+//   - a second expunge of the same message could push a counter below zero.
+//
+// These tests state what must hold after any operation and run every operation
+// through each path that can perform it. They do not care which code did the
+// work, only that the result is the same.
+
+// folderState is everything observable about one folder.
+type folderState struct {
+	Name          string
+	CachedTotal   int
+	CachedUnread  int
+	RealTotal     int
+	RealUnread    int
+	HighestModSeq int64
+	UIDNext       int64
+	MaxMessageSeq int64
+}
+
+// mailState reads the cached and the real numbers side by side.
+func mailState(t *testing.T, pool *pgxpool.Pool, mailboxID string) (folders map[string]folderState, usedBytes, realBytes int64) {
+	t.Helper()
+	ctx := context.Background()
+
+	rows, err := pool.Query(ctx, `
+		SELECT f.name, f.total_count, f.unread_count, f.highest_modseq, f.uid_next,
+		       COUNT(e.id)::int,
+		       COUNT(e.id) FILTER (WHERE NOT EXISTS (
+		           SELECT 1 FROM message_flags mf
+		            WHERE mf.message_id = e.id AND mf.received_at = e.received_at AND mf.flag = '\Seen'))::int,
+		       COALESCE(MAX(e.modseq), 0)
+		  FROM folders f
+		  LEFT JOIN email_messages e ON e.folder_id = f.id AND e.expunged_at IS NULL
+		 WHERE f.mailbox_id = $1
+		 GROUP BY f.id`, mailboxID)
+	if err != nil {
+		t.Fatalf("read folder state: %v", err)
+	}
+	defer rows.Close()
+
+	folders = map[string]folderState{}
+	for rows.Next() {
+		var s folderState
+		if err := rows.Scan(&s.Name, &s.CachedTotal, &s.CachedUnread, &s.HighestModSeq, &s.UIDNext, &s.RealTotal, &s.RealUnread, &s.MaxMessageSeq); err != nil {
+			t.Fatalf("scan folder state: %v", err)
+		}
+		folders[s.Name] = s
+	}
+
+	if err := pool.QueryRow(ctx, `SELECT used_bytes FROM mailboxes WHERE id = $1`, mailboxID).Scan(&usedBytes); err != nil {
+		t.Fatalf("read used_bytes: %v", err)
+	}
+	if err := pool.QueryRow(ctx, `SELECT COALESCE(SUM(size_bytes), 0) FROM email_messages WHERE mailbox_id = $1 AND expunged_at IS NULL`, mailboxID).Scan(&realBytes); err != nil {
+		t.Fatalf("read real bytes: %v", err)
+	}
+	return folders, usedBytes, realBytes
+}
+
+// assertConsistent is the contract: every cached number equals what the rows say.
+func assertConsistent(t *testing.T, pool *pgxpool.Pool, mailboxID, after string) {
+	t.Helper()
+	folders, used, real := mailState(t, pool, mailboxID)
+
+	for name, f := range folders {
+		if f.CachedTotal != f.RealTotal {
+			t.Errorf("after %s: %s total_count = %d, but it holds %d messages", after, name, f.CachedTotal, f.RealTotal)
+		}
+		if f.CachedUnread != f.RealUnread {
+			t.Errorf("after %s: %s unread_count = %d, but %d messages are unread", after, name, f.CachedUnread, f.RealUnread)
+		}
+		if f.CachedUnread < 0 || f.CachedTotal < 0 {
+			t.Errorf("after %s: %s has a negative counter (unread %d, total %d)", after, name, f.CachedUnread, f.CachedTotal)
+		}
+		if f.HighestModSeq < f.MaxMessageSeq {
+			t.Errorf("after %s: %s highest_modseq %d is behind a message's modseq %d, so a CONDSTORE client would miss the change", after, name, f.HighestModSeq, f.MaxMessageSeq)
+		}
+	}
+	if used != real {
+		t.Errorf("after %s: mailbox used_bytes = %d, but its messages add up to %d", after, used, real)
+	}
+}
+
+// modseqOf is the folder's highest_modseq, which every observable change must raise.
+func modseqOf(t *testing.T, pool *pgxpool.Pool, mailboxID, folder string) int64 {
+	t.Helper()
+	folders, _, _ := mailState(t, pool, mailboxID)
+	return folders[folder].HighestModSeq
+}
+
+func folderID(t *testing.T, pool *pgxpool.Pool, mailboxID, name string) string {
+	t.Helper()
+	var id string
+	if err := pool.QueryRow(context.Background(), `SELECT id::text FROM folders WHERE mailbox_id = $1 AND name = $2`, mailboxID, name).Scan(&id); err != nil {
+		t.Fatalf("find folder %s: %v", name, err)
+	}
+	return id
+}
+
+// path is one way of doing each thing to a message. IMAP and webmail both
+// implement it; the contract runs against each.
+type path struct {
+	name      string
+	setSeen   func(t *testing.T, pool *pgxpool.Pool, mailboxID, folder string, uid uint32, seen bool)
+	setFlag   func(t *testing.T, pool *pgxpool.Pool, mailboxID, folder string, uid uint32, flagged bool)
+	expunge   func(t *testing.T, pool *pgxpool.Pool, mailboxID, folder string, uid uint32)
+	moveTo    func(t *testing.T, pool *pgxpool.Pool, mailboxID, folder string, uid uint32, target string)
+	flagsKept func() bool
+}
+
+func imapPath() path {
+	return path{
+		name: "imap",
+		setSeen: func(t *testing.T, pool *pgxpool.Pool, mailboxID, folder string, uid uint32, seen bool) {
+			op := port.FlagOpAdd
+			if !seen {
+				op = port.FlagOpDel
+			}
+			if _, err := NewFlagRepository(pool).SetFlags(context.Background(), folderID(t, pool, mailboxID, folder), uid, op, []string{`\Seen`}, 0); err != nil {
+				t.Fatalf("imap SetFlags: %v", err)
+			}
+		},
+		setFlag: func(t *testing.T, pool *pgxpool.Pool, mailboxID, folder string, uid uint32, flagged bool) {
+			op := port.FlagOpAdd
+			if !flagged {
+				op = port.FlagOpDel
+			}
+			if _, err := NewFlagRepository(pool).SetFlags(context.Background(), folderID(t, pool, mailboxID, folder), uid, op, []string{`\Flagged`}, 0); err != nil {
+				t.Fatalf("imap SetFlags: %v", err)
+			}
+		},
+		expunge: func(t *testing.T, pool *pgxpool.Pool, mailboxID, folder string, uid uint32) {
+			if err := NewExpungeRepository(pool).Expunge(context.Background(), folderID(t, pool, mailboxID, folder), []uint32{uid}); err != nil {
+				t.Fatalf("imap Expunge: %v", err)
+			}
+		},
+		moveTo: func(t *testing.T, pool *pgxpool.Pool, mailboxID, folder string, uid uint32, target string) {
+			// IMAP has no MOVE here: a client copies, marks \Deleted and expunges
+			src, dst := folderID(t, pool, mailboxID, folder), folderID(t, pool, mailboxID, target)
+			if _, err := NewCopyRepository(pool).CopyMessages(context.Background(), src, []uint32{uid}, dst); err != nil {
+				t.Fatalf("imap Copy: %v", err)
+			}
+			if err := NewExpungeRepository(pool).Expunge(context.Background(), src, []uint32{uid}); err != nil {
+				t.Fatalf("imap Expunge after copy: %v", err)
+			}
+		},
+	}
+}
+
+func webmailPath() path {
+	return path{
+		name: "webmail",
+		setSeen: func(t *testing.T, pool *pgxpool.Pool, mailboxID, folder string, uid uint32, seen bool) {
+			if err := NewWebmailRepository(pool).MarkSeen(context.Background(), mailboxID, folder, uid, seen); err != nil {
+				t.Fatalf("webmail MarkSeen: %v", err)
+			}
+		},
+		setFlag: func(t *testing.T, pool *pgxpool.Pool, mailboxID, folder string, uid uint32, flagged bool) {
+			if err := NewWebmailRepository(pool).MarkFlagged(context.Background(), mailboxID, folder, uid, flagged); err != nil {
+				t.Fatalf("webmail MarkFlagged: %v", err)
+			}
+		},
+		expunge: func(t *testing.T, pool *pgxpool.Pool, mailboxID, folder string, uid uint32) {
+			if err := NewWebmailRepository(pool).Expunge(context.Background(), mailboxID, folder, uid); err != nil {
+				t.Fatalf("webmail Expunge: %v", err)
+			}
+		},
+		moveTo: func(t *testing.T, pool *pgxpool.Pool, mailboxID, folder string, uid uint32, target string) {
+			if _, err := NewWebmailRepository(pool).MoveToFolder(context.Background(), mailboxID, folder, uid, target); err != nil {
+				t.Fatalf("webmail Move: %v", err)
+			}
+		},
+	}
+}
+
+func eachPath(t *testing.T, scenario func(t *testing.T, p path)) {
+	for _, p := range []path{imapPath(), webmailPath()} {
+		p := p
+		t.Run(p.name, func(t *testing.T) { scenario(t, p) })
+	}
+}
+
+func TestContract_ReadingAMessageMovesTheUnreadCounter(t *testing.T) {
+	pool := testPool(t)
+	eachPath(t, func(t *testing.T, p path) {
+		mailboxID := seedMailbox(t, pool)
+		a := deliver(t, pool, mailboxID, "INBOX", "a", false)
+		deliver(t, pool, mailboxID, "INBOX", "b", false)
+		assertConsistent(t, pool, mailboxID, "delivery")
+
+		before := modseqOf(t, pool, mailboxID, "INBOX")
+		p.setSeen(t, pool, mailboxID, "INBOX", a, true)
+		assertConsistent(t, pool, mailboxID, "marking one message read")
+		if after := modseqOf(t, pool, mailboxID, "INBOX"); after <= before {
+			t.Errorf("marking read left highest_modseq at %d (was %d): clients holding the folder never learn of it", after, before)
+		}
+
+		p.setSeen(t, pool, mailboxID, "INBOX", a, true)
+		assertConsistent(t, pool, mailboxID, "marking the same message read twice")
+
+		p.setSeen(t, pool, mailboxID, "INBOX", a, false)
+		assertConsistent(t, pool, mailboxID, "marking it unread again")
+	})
+}
+
+func TestContract_FlaggingBumpsTheModseqAndNothingElse(t *testing.T) {
+	pool := testPool(t)
+	eachPath(t, func(t *testing.T, p path) {
+		mailboxID := seedMailbox(t, pool)
+		a := deliver(t, pool, mailboxID, "INBOX", "a", false)
+
+		before := modseqOf(t, pool, mailboxID, "INBOX")
+		p.setFlag(t, pool, mailboxID, "INBOX", a, true)
+		assertConsistent(t, pool, mailboxID, "flagging")
+		if after := modseqOf(t, pool, mailboxID, "INBOX"); after <= before {
+			t.Errorf("flagging left highest_modseq at %d (was %d)", after, before)
+		}
+		p.setFlag(t, pool, mailboxID, "INBOX", a, false)
+		assertConsistent(t, pool, mailboxID, "unflagging")
+	})
+}
+
+func TestContract_DeletingFreesTheQuotaAndTheCounters(t *testing.T) {
+	pool := testPool(t)
+	eachPath(t, func(t *testing.T, p path) {
+		mailboxID := seedMailbox(t, pool)
+		unread := deliver(t, pool, mailboxID, "INBOX", "unread", false)
+		read := deliver(t, pool, mailboxID, "INBOX", "read", true)
+		assertConsistent(t, pool, mailboxID, "delivery")
+
+		p.expunge(t, pool, mailboxID, "INBOX", unread)
+		assertConsistent(t, pool, mailboxID, "deleting an unread message")
+
+		p.expunge(t, pool, mailboxID, "INBOX", read)
+		assertConsistent(t, pool, mailboxID, "deleting a read message")
+
+		_, used, _ := mailState(t, pool, mailboxID)
+		if used != 0 {
+			t.Errorf("an emptied mailbox still reports %d used bytes", used)
+		}
+	})
+}
+
+func TestContract_AMessageAlreadyDeletedCannotDriveACounterNegative(t *testing.T) {
+	pool := testPool(t)
+	eachPath(t, func(t *testing.T, p path) {
+		mailboxID := seedMailbox(t, pool)
+		a := deliver(t, pool, mailboxID, "INBOX", "a", false)
+		deliver(t, pool, mailboxID, "INBOX", "b", false)
+
+		p.expunge(t, pool, mailboxID, "INBOX", a)
+		// The second one is the same message again. The webmail reports it as
+		// not found; IMAP ignores it. Either way no number may move.
+		func() {
+			defer func() { _ = recover() }()
+			expungeAgain(t, pool, p, mailboxID, a)
+		}()
+		assertConsistent(t, pool, mailboxID, "deleting the same message twice")
+	})
+}
+
+// expungeAgain tolerates the webmail's "not found" while still letting the
+// contract check the counters afterwards.
+func expungeAgain(t *testing.T, pool *pgxpool.Pool, p path, mailboxID string, uid uint32) {
+	t.Helper()
+	switch p.name {
+	case "imap":
+		_ = NewExpungeRepository(pool).Expunge(context.Background(), folderID(t, pool, mailboxID, "INBOX"), []uint32{uid})
+	default:
+		_ = NewWebmailRepository(pool).Expunge(context.Background(), mailboxID, "INBOX", uid)
+	}
+}
+
+func TestContract_MovingAMessageKeepsBothFoldersTrue(t *testing.T) {
+	pool := testPool(t)
+	eachPath(t, func(t *testing.T, p path) {
+		mailboxID := seedMailbox(t, pool)
+		unread := deliver(t, pool, mailboxID, "INBOX", "unread", false)
+		read := deliver(t, pool, mailboxID, "INBOX", "read", true)
+
+		p.moveTo(t, pool, mailboxID, "INBOX", unread, "Trash")
+		assertConsistent(t, pool, mailboxID, "moving an unread message")
+		p.moveTo(t, pool, mailboxID, "INBOX", read, "Trash")
+		assertConsistent(t, pool, mailboxID, "moving a read message")
+
+		folders, _, _ := mailState(t, pool, mailboxID)
+		if folders["INBOX"].RealTotal != 0 || folders["Trash"].RealTotal != 2 {
+			t.Errorf("INBOX holds %d and Trash %d, want 0 and 2", folders["INBOX"].RealTotal, folders["Trash"].RealTotal)
+		}
+	})
+}
+
+// Reading mail over IMAP and then looking at it in the webmail (or the other way
+// round) is the everyday case: the two views must agree after every step.
+func TestContract_ImapAndWebmailAgreeOnTheSameMailbox(t *testing.T) {
+	pool := testPool(t)
+	imap, web := imapPath(), webmailPath()
+
+	mailboxID := seedMailbox(t, pool)
+	var uids []uint32
+	for i := 0; i < 5; i++ {
+		uids = append(uids, deliver(t, pool, mailboxID, "INBOX", fmt.Sprintf("m%d", i), false))
+	}
+
+	imap.setSeen(t, pool, mailboxID, "INBOX", uids[0], true)
+	assertConsistent(t, pool, mailboxID, "reading m0 over IMAP")
+	web.setSeen(t, pool, mailboxID, "INBOX", uids[1], true)
+	assertConsistent(t, pool, mailboxID, "reading m1 in the webmail")
+	imap.setFlag(t, pool, mailboxID, "INBOX", uids[2], true)
+	web.expunge(t, pool, mailboxID, "INBOX", uids[3])
+	assertConsistent(t, pool, mailboxID, "deleting m3 in the webmail")
+	imap.expunge(t, pool, mailboxID, "INBOX", uids[1])
+	assertConsistent(t, pool, mailboxID, "deleting the already-read m1 over IMAP")
+	web.moveTo(t, pool, mailboxID, "INBOX", uids[4], "Trash")
+	assertConsistent(t, pool, mailboxID, "moving m4 to Trash in the webmail")
+	imap.moveTo(t, pool, mailboxID, "INBOX", uids[2], "Trash")
+	assertConsistent(t, pool, mailboxID, "moving m2 to Trash over IMAP")
+
+	// What the webmail reports for a folder is what IMAP would answer
+	ctx := context.Background()
+	wmFolders, err := NewWebmailRepository(pool).ListFolders(ctx, mailboxID)
+	if err != nil {
+		t.Fatalf("webmail ListFolders: %v", err)
+	}
+	imFolders, err := NewImapFolderRepository(pool).ListFolders(ctx, mailboxID)
+	if err != nil {
+		t.Fatalf("imap ListFolders: %v", err)
+	}
+	imapTotals := map[string]int{}
+	for _, f := range imFolders {
+		imapTotals[f.Name] = int(f.NumMessages)
+	}
+	for _, f := range wmFolders {
+		if got := imapTotals[f.Name]; got != f.TotalCount {
+			t.Errorf("%s: the webmail shows %d messages and IMAP says %d", f.Name, f.TotalCount, got)
+		}
+	}
+}
+
+// A folder deleted by its owner takes its messages with it, and their bytes.
+func TestContract_DeletingAFolderReturnsItsBytes(t *testing.T) {
+	pool := testPool(t)
+	ctx := context.Background()
+	mailboxID := seedMailbox(t, pool)
+	repo := NewWebmailRepository(pool)
+
+	if err := repo.CreateFolder(ctx, mailboxID, "Projetos"); err != nil {
+		t.Fatalf("create folder: %v", err)
+	}
+	deliver(t, pool, mailboxID, "Projetos", "one", false)
+	deliver(t, pool, mailboxID, "Projetos", "two", true)
+	deliver(t, pool, mailboxID, "INBOX", "stays", false)
+	assertConsistent(t, pool, mailboxID, "filing into a new folder")
+
+	if err := repo.DeleteFolder(ctx, mailboxID, "Projetos"); err != nil {
+		t.Fatalf("delete folder: %v", err)
+	}
+	assertConsistent(t, pool, mailboxID, "deleting the folder")
+}
+
+// IMAP's STORE can replace a message's whole flag set; the unread counter has to
+// follow the \Seen that comes or goes with it.
+func TestContract_ReplacingTheFlagSetKeepsTheUnreadCounterTrue(t *testing.T) {
+	pool := testPool(t)
+	ctx := context.Background()
+	mailboxID := seedMailbox(t, pool)
+	a := deliver(t, pool, mailboxID, "INBOX", "a", false)
+	b := deliver(t, pool, mailboxID, "INBOX", "b", true)
+	inbox := folderID(t, pool, mailboxID, "INBOX")
+	repo := NewFlagRepository(pool)
+
+	if _, err := repo.SetFlags(ctx, inbox, a, port.FlagOpSet, []string{`\Seen`, `\Flagged`}, 0); err != nil {
+		t.Fatalf("SetFlags: %v", err)
+	}
+	assertConsistent(t, pool, mailboxID, "replacing flags with one that includes \\Seen")
+
+	if _, err := repo.SetFlags(ctx, inbox, b, port.FlagOpSet, []string{`\Flagged`}, 0); err != nil {
+		t.Fatalf("SetFlags: %v", err)
+	}
+	assertConsistent(t, pool, mailboxID, "replacing flags with one that drops \\Seen")
+}
+
+var _ = uuid.Nil
+
+// IMAP clients, the webmail and the delivery path all touch a mailbox at the same
+// moment. The counters are shared rows, so they have to stay true under that.
+func TestContract_ConcurrentChangesFromBothPathsKeepTheCountersTrue(t *testing.T) {
+	pool := testPool(t)
+	mailboxID := seedMailbox(t, pool)
+
+	const n = 24
+	uids := make([]uint32, 0, n)
+	for i := 0; i < n; i++ {
+		uids = append(uids, deliver(t, pool, mailboxID, "INBOX", fmt.Sprintf("m%d", i), false))
+	}
+
+	imap, web := imapPath(), webmailPath()
+	done := make(chan struct{}, n)
+	for i, uid := range uids {
+		go func(i int, uid uint32) {
+			defer func() { done <- struct{}{} }()
+			switch i % 3 {
+			case 0:
+				imap.setSeen(t, pool, mailboxID, "INBOX", uid, true)
+			case 1:
+				web.setSeen(t, pool, mailboxID, "INBOX", uid, true)
+			default:
+				if i%2 == 0 {
+					imap.expunge(t, pool, mailboxID, "INBOX", uid)
+				} else {
+					web.expunge(t, pool, mailboxID, "INBOX", uid)
+				}
+			}
+		}(i, uid)
+	}
+	for range uids {
+		<-done
+	}
+
+	assertConsistent(t, pool, mailboxID, "24 concurrent changes from IMAP and the webmail")
+}
+
+// Two clients deleting the same message at once is the realistic race (the
+// webmail and a phone both open on the same mail). It is removed once, and every
+// number moves once.
+func TestContract_DeletingTheSameMessageConcurrentlyCountsOnce(t *testing.T) {
+	pool := testPool(t)
+	mailboxID := seedMailbox(t, pool)
+	target := deliver(t, pool, mailboxID, "INBOX", "contested", false)
+	deliver(t, pool, mailboxID, "INBOX", "bystander", false)
+	inbox := folderID(t, pool, mailboxID, "INBOX")
+
+	ctx := context.Background()
+	store := NewMailStore(pool)
+	removed := make(chan int, 12)
+	for i := 0; i < 12; i++ {
+		go func() {
+			n, err := store.Expunge(ctx, inbox, []uint32{target})
+			if err != nil {
+				t.Errorf("expunge: %v", err)
+			}
+			removed <- n
+		}()
+	}
+	total := 0
+	for i := 0; i < 12; i++ {
+		total += <-removed
+	}
+
+	if total != 1 {
+		t.Errorf("12 concurrent expunges of one message removed it %d times, want exactly once", total)
+	}
+	assertConsistent(t, pool, mailboxID, "12 clients deleting the same message")
+	folders, used, _ := mailState(t, pool, mailboxID)
+	if folders["INBOX"].RealTotal != 1 || used != 10 {
+		t.Errorf("INBOX holds %d and the mailbox %d bytes, want 1 message and 10 bytes", folders["INBOX"].RealTotal, used)
+	}
+}
+
+// Moves in opposite directions, flag changes and deletes, all at once on the same
+// two folders. Locking the folders and the message in different orders in
+// different operations deadlocks here; a fixed order does not.
+func TestContract_OppositeMovesAndFlagChangesNeverDeadlock(t *testing.T) {
+	pool := testPool(t)
+	mailboxID := seedMailbox(t, pool)
+
+	const each = 20
+	var inboxUIDs, trashUIDs []uint32
+	for i := 0; i < each; i++ {
+		inboxUIDs = append(inboxUIDs, deliver(t, pool, mailboxID, "INBOX", fmt.Sprintf("i%d", i), false))
+		trashUIDs = append(trashUIDs, deliver(t, pool, mailboxID, "Trash", fmt.Sprintf("t%d", i), false))
+	}
+
+	inbox, trash := folderID(t, pool, mailboxID, "INBOX"), folderID(t, pool, mailboxID, "Trash")
+	store := NewMailStore(pool)
+	ctx := context.Background()
+
+	errs := make(chan error, each*4)
+	var pending int
+	run := func(f func() error) {
+		pending++
+		go func() { errs <- f() }()
+	}
+	for i := 0; i < each; i++ {
+		i := i
+		run(func() error { _, err := store.Move(ctx, inbox, inboxUIDs[i], trash); return nil2(err) })
+		run(func() error { _, err := store.Move(ctx, trash, trashUIDs[i], inbox); return nil2(err) })
+		// a flag change on a message that is being moved elsewhere, and a delete
+		run(func() error {
+			_, err := store.SetFlags(ctx, inbox, inboxUIDs[(i+1)%each], port.FlagOpAdd, []string{`\Flagged`}, 0)
+			return nil2(err)
+		})
+		run(func() error { _, err := store.Expunge(ctx, trash, []uint32{trashUIDs[(i+2)%each]}); return nil2(err) })
+	}
+	for ; pending > 0; pending-- {
+		if err := <-errs; err != nil {
+			t.Errorf("a concurrent operation failed (a deadlock, if it says 40P01): %v", err)
+		}
+	}
+
+	assertConsistent(t, pool, mailboxID, "opposite moves, flag changes and deletes all at once")
+}
+
+// nil2 lets the contract tolerate "the message was moved or deleted first", a
+// legitimate outcome of a race, while still surfacing every other error (above
+// all a deadlock, SQLSTATE 40P01).
+func nil2(err error) error {
+	if err == ErrMessageNotFound {
+		return nil
+	}
+	return err
+}
diff --git a/services/protocols/internal/infrastructure/postgres/mail_store.go b/services/protocols/internal/infrastructure/postgres/mail_store.go
new file mode 100644
index 0000000..1a0fb30
--- /dev/null
+++ b/services/protocols/internal/infrastructure/postgres/mail_store.go
@@ -0,0 +1,486 @@
+package postgres
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"sort"
+
+	"github.com/google/uuid"
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgxpool"
+
+	"lambdamail/protocols/internal/application/port"
+)
+
+// MailStore is the one place that changes the state of messages and folders.
+//
+// IMAP, POP3, the webmail and the server's own filing all end up changing the
+// same rows, and those rows carry cached numbers that have to stay true: the
+// folder's unread and total counters, its highest modseq (what a CONDSTORE
+// client uses to learn that something changed), the next UID, and the
+// mailbox's used bytes. When each path implemented this on its own they
+// drifted apart - reading over IMAP never moved the unread counter, deleting in
+// the webmail never gave the quota back, a repeated expunge could push a
+// counter below zero - and every fix had to be made twice, which is how one of
+// the two went missing.
+//
+// So each state change is written here, once, in one transaction, and every
+// path calls it. The repositories IMAP and the webmail used are now thin
+// adapters over this: they translate their way of naming things (a folder id
+// and a UID, or a mailbox, a folder name and a UID) and nothing else.
+//
+// Rules held for every method:
+//
+//   - A counter never goes below zero, so a double operation cannot corrupt it.
+//   - An operation that changes what a client can observe raises the folder's
+//     modseq; one that changes nothing does not.
+//   - A message is located by folder, so another mailbox's mail cannot be
+//     reached by guessing a UID.
+type MailStore struct {
+	pool *pgxpool.Pool
+}
+
+func NewMailStore(pool *pgxpool.Pool) *MailStore {
+	return &MailStore{pool: pool}
+}
+
+// lockFolders takes the row lock of each folder, in a fixed order.
+//
+// Every change updates counters on a folder row, and a move updates two. If one
+// operation locked the destination folder and then the source, and another did
+// the reverse, two moves in opposite directions deadlocked, and so did a move
+// racing a flag change (it held the message and wanted the folder, the move held
+// the folder and wanted the message). So the order is the same everywhere:
+// folders first, lowest id first, then the message.
+func lockFolders(ctx context.Context, tx pgx.Tx, ids ...string) error {
+	sort.Strings(ids)
+	for i, id := range ids {
+		if i > 0 && id == ids[i-1] {
+			continue
+		}
+		if _, err := tx.Exec(ctx, `SELECT 1 FROM folders WHERE id = $1 FOR UPDATE`, id); err != nil {
+			return fmt.Errorf("lock folder %s: %w", id, err)
+		}
+	}
+	return nil
+}
+
+// messageRow is the slice of a message every operation needs.
+type messageRow struct {
+	ID         uuid.UUID
+	ReceivedAt any
+	MailboxID  string
+	Size       int64
+	ModSeq     uint64
+	Seen       bool
+}
+
+// loadMessage finds a live message by folder and UID and locks it, so two
+// concurrent changes to the same message cannot both read the old state.
+func loadMessage(ctx context.Context, tx pgx.Tx, folderID string, uid uint32) (*messageRow, error) {
+	var m messageRow
+	err := tx.QueryRow(ctx, `
+		SELECT e.id, e.received_at, e.mailbox_id::text, e.size_bytes, e.modseq,
+		       EXISTS (SELECT 1 FROM message_flags mf
+		                WHERE mf.message_id = e.id AND mf.received_at = e.received_at AND mf.flag = '\Seen')
+		  FROM email_messages e
+		 WHERE e.folder_id = $1 AND e.uid = $2 AND e.expunged_at IS NULL
+		   FOR UPDATE
+	`, folderID, int64(uid)).Scan(&m.ID, &m.ReceivedAt, &m.MailboxID, &m.Size, &m.ModSeq, &m.Seen)
+	if errors.Is(err, pgx.ErrNoRows) {
+		return nil, ErrMessageNotFound
+	}
+	if err != nil {
+		return nil, fmt.Errorf("find message folder=%s uid=%d: %w", folderID, uid, err)
+	}
+	return &m, nil
+}
+
+// ResolveFolder finds a folder of a mailbox by its special-use role or by its
+// name, the way the webmail and IMAP clients both address one ("trash" and
+// "Trash" reach the same place; a folder the user made has no role and is
+// reached by name). port.ErrFolderMissing when there is none.
+func (s *MailStore) ResolveFolder(ctx context.Context, mailboxID, ref string) (string, error) {
+	var id string
+	err := s.pool.QueryRow(ctx, `
+		SELECT id::text FROM folders
+		 WHERE mailbox_id = $1 AND (special_use = LOWER($2) OR LOWER(name) = LOWER($2))
+		 ORDER BY special_use IS NOT NULL DESC
+		 LIMIT 1
+	`, mailboxID, ref).Scan(&id)
+	if errors.Is(err, pgx.ErrNoRows) {
+		return "", port.ErrFolderMissing
+	}
+	return id, err
+}
+
+// SetFlags applies op to one message's flags. Add and Del touch individual
+// flags, Set replaces the whole set. If unchangedSince > 0 and the message has
+// changed since, nothing is written and updated is false (RFC 7162
+// UNCHANGEDSINCE).
+//
+// \Seen is the flag with a side effect: the folder's unread counter follows it,
+// in the same transaction, by looking at the flag before and after rather than
+// at which operation was asked for. That is what keeps STORE +FLAGS, STORE
+// -FLAGS, STORE FLAGS (replace) and the webmail's mark-as-read all counting the
+// same way.
+func (s *MailStore) SetFlags(ctx context.Context, folderID string, uid uint32, op port.FlagOp, flags []string, unchangedSince uint64) (bool, error) {
+	tx, err := s.pool.Begin(ctx)
+	if err != nil {
+		return false, fmt.Errorf("begin transaction: %w", err)
+	}
+	defer tx.Rollback(ctx)
+
+	if err := lockFolders(ctx, tx, folderID); err != nil {
+		return false, err
+	}
+	msg, err := loadMessage(ctx, tx, folderID, uid)
+	if err != nil {
+		return false, err
+	}
+
+	if unchangedSince > 0 && msg.ModSeq > unchangedSince {
+		return false, nil
+	}
+
+	before, err := flagSet(ctx, tx, msg)
+	if err != nil {
+		return false, err
+	}
+
+	switch op {
+	case port.FlagOpAdd:
+		for _, flag := range flags {
+			if _, err := tx.Exec(ctx, `
+				INSERT INTO message_flags (message_id, received_at, flag) VALUES ($1, $2, $3)
+				ON CONFLICT DO NOTHING`, msg.ID, msg.ReceivedAt, flag); err != nil {
+				return false, fmt.Errorf("add flag %q: %w", flag, err)
+			}
+		}
+	case port.FlagOpDel:
+		for _, flag := range flags {
+			if _, err := tx.Exec(ctx, `
+				DELETE FROM message_flags WHERE message_id = $1 AND received_at = $2 AND flag = $3`,
+				msg.ID, msg.ReceivedAt, flag); err != nil {
+				return false, fmt.Errorf("delete flag %q: %w", flag, err)
+			}
+		}
+	case port.FlagOpSet:
+		if _, err := tx.Exec(ctx, `
+			DELETE FROM message_flags WHERE message_id = $1 AND received_at = $2`, msg.ID, msg.ReceivedAt); err != nil {
+			return false, fmt.Errorf("clear flags before set: %w", err)
+		}
+		for _, flag := range flags {
+			if _, err := tx.Exec(ctx, `
+				INSERT INTO message_flags (message_id, received_at, flag) VALUES ($1, $2, $3)
+				ON CONFLICT DO NOTHING`, msg.ID, msg.ReceivedAt, flag); err != nil {
+				return false, fmt.Errorf("set flag %q: %w", flag, err)
+			}
+		}
+	}
+
+	after, err := flagSet(ctx, tx, msg)
+	if err != nil {
+		return false, err
+	}
+
+	// Nothing changed: no modseq, no counter. A client that stores a flag the
+	// message already has must not be told the folder changed.
+	if sameFlags(before, after) {
+		return true, tx.Commit(ctx)
+	}
+
+	unreadDelta := 0
+	switch {
+	case before[`\Seen`] && !after[`\Seen`]:
+		unreadDelta = 1
+	case !before[`\Seen`] && after[`\Seen`]:
+		unreadDelta = -1
+	}
+
+	var modseq int64
+	if err := tx.QueryRow(ctx, `
+		UPDATE folders
+		   SET highest_modseq = highest_modseq + 1,
+		       unread_count = GREATEST(0, unread_count + $2)
+		 WHERE id = $1
+		RETURNING highest_modseq`, folderID, unreadDelta).Scan(&modseq); err != nil {
+		return false, fmt.Errorf("advance folder modseq: %w", err)
+	}
+	if _, err := tx.Exec(ctx, `UPDATE email_messages SET modseq = $3 WHERE id = $1 AND received_at = $2`,
+		msg.ID, msg.ReceivedAt, modseq); err != nil {
+		return false, fmt.Errorf("update message modseq: %w", err)
+	}
+
+	return true, tx.Commit(ctx)
+}
+
+func flagSet(ctx context.Context, tx pgx.Tx, msg *messageRow) (map[string]bool, error) {
+	rows, err := tx.Query(ctx, `SELECT flag FROM message_flags WHERE message_id = $1 AND received_at = $2`, msg.ID, msg.ReceivedAt)
+	if err != nil {
+		return nil, fmt.Errorf("read flags: %w", err)
+	}
+	defer rows.Close()
+	set := map[string]bool{}
+	for rows.Next() {
+		var f string
+		if err := rows.Scan(&f); err != nil {
+			return nil, err
+		}
+		set[f] = true
+	}
+	return set, rows.Err()
+}
+
+func sameFlags(a, b map[string]bool) bool {
+	if len(a) != len(b) {
+		return false
+	}
+	for k := range a {
+		if !b[k] {
+			return false
+		}
+	}
+	return true
+}
+
+// Expunge removes messages from a folder (soft delete: the row stays, marked,
+// and the blob stays referenced until the retention sweep, so a mistake is
+// recoverable and a client holding the UID still resolves it).
+//
+// For each message that was really there it lowers the folder's total, lowers
+// unread if the message was unread, and gives its bytes back to the mailbox's
+// quota. A message that is already gone is skipped, touching nothing, which is
+// what makes a repeated expunge safe. It returns how many messages were
+// removed.
+func (s *MailStore) Expunge(ctx context.Context, folderID string, uids []uint32) (int, error) {
+	if len(uids) == 0 {
+		return 0, nil
+	}
+	tx, err := s.pool.Begin(ctx)
+	if err != nil {
+		return 0, fmt.Errorf("begin transaction: %w", err)
+	}
+	defer tx.Rollback(ctx)
+
+	if err := lockFolders(ctx, tx, folderID); err != nil {
+		return 0, err
+	}
+
+	removed := 0
+	for _, uid := range uids {
+		msg, err := loadMessage(ctx, tx, folderID, uid)
+		if errors.Is(err, ErrMessageNotFound) {
+			continue
+		}
+		if err != nil {
+			return 0, err
+		}
+
+		if _, err := tx.Exec(ctx, `UPDATE email_messages SET expunged_at = NOW() WHERE id = $1 AND received_at = $2`,
+			msg.ID, msg.ReceivedAt); err != nil {
+			return 0, fmt.Errorf("expunge uid %d: %w", uid, err)
+		}
+
+		unreadDelta := 0
+		if !msg.Seen {
+			unreadDelta = -1
+		}
+		if _, err := tx.Exec(ctx, `
+			UPDATE folders
+			   SET total_count = GREATEST(0, total_count - 1),
+			       unread_count = GREATEST(0, unread_count + $2),
+			       highest_modseq = highest_modseq + 1
+			 WHERE id = $1`, folderID, unreadDelta); err != nil {
+			return 0, fmt.Errorf("lower folder counters for uid %d: %w", uid, err)
+		}
+
+		if _, err := tx.Exec(ctx, `UPDATE mailboxes SET used_bytes = GREATEST(0, used_bytes - $1) WHERE id = $2`,
+			msg.Size, msg.MailboxID); err != nil {
+			return 0, fmt.Errorf("give quota back for uid %d: %w", uid, err)
+		}
+		removed++
+	}
+
+	return removed, tx.Commit(ctx)
+}
+
+// Move relocates one message to another folder of the same mailbox and returns
+// the UID it has there. The message keeps its identity, its flags and its blob;
+// only the folder and the UID change, because a UID means something only inside
+// one folder. The quota does not move: the bytes stay in the same mailbox.
+func (s *MailStore) Move(ctx context.Context, sourceFolderID string, uid uint32, destFolderID string) (uint32, error) {
+	tx, err := s.pool.Begin(ctx)
+	if err != nil {
+		return 0, err
+	}
+	defer tx.Rollback(ctx)
+
+	if err := lockFolders(ctx, tx, sourceFolderID, destFolderID); err != nil {
+		return 0, err
+	}
+	msg, err := loadMessage(ctx, tx, sourceFolderID, uid)
+	if err != nil {
+		return 0, err
+	}
+
+	var destUID int64
+	if err := tx.QueryRow(ctx, `SELECT uid_next FROM folders WHERE id = $1`, destFolderID).Scan(&destUID); err != nil {
+		return 0, fmt.Errorf("read destination uid: %w", err)
+	}
+
+	unread := 0
+	if !msg.Seen {
+		unread = 1
+	}
+
+	var modseq int64
+	if err := tx.QueryRow(ctx, `
+		UPDATE folders
+		   SET uid_next = uid_next + 1, highest_modseq = highest_modseq + 1,
+		       total_count = total_count + 1, unread_count = unread_count + $2
+		 WHERE id = $1
+		RETURNING highest_modseq`, destFolderID, unread).Scan(&modseq); err != nil {
+		return 0, fmt.Errorf("advance destination folder: %w", err)
+	}
+
+	if _, err := tx.Exec(ctx, `UPDATE email_messages SET folder_id = $3, uid = $4, modseq = $5 WHERE id = $1 AND received_at = $2`,
+		msg.ID, msg.ReceivedAt, destFolderID, destUID, modseq); err != nil {
+		return 0, fmt.Errorf("move message: %w", err)
+	}
+
+	if _, err := tx.Exec(ctx, `
+		UPDATE folders
+		   SET total_count = GREATEST(0, total_count - 1),
+		       unread_count = GREATEST(0, unread_count - $2),
+		       highest_modseq = highest_modseq + 1
+		 WHERE id = $1`, sourceFolderID, unread); err != nil {
+		return 0, fmt.Errorf("lower source folder counters: %w", err)
+	}
+
+	return uint32(destUID), tx.Commit(ctx)
+}
+
+// Copy duplicates messages into another folder. Each copy is its own message
+// (own UID, own flags copied from the original) that shares the original's
+// blob, and it counts against the quota like any other message. One transaction
+// per message, so a failure part-way leaves the earlier copies whole.
+func (s *MailStore) Copy(ctx context.Context, sourceFolderID string, uids []uint32, destFolderID string) ([]port.CopiedMessage, error) {
+	results := make([]port.CopiedMessage, 0, len(uids))
+	for _, uid := range uids {
+		destUID, err := s.copyOne(ctx, sourceFolderID, uid, destFolderID)
+		if err != nil {
+			return nil, fmt.Errorf("copy uid %d: %w", uid, err)
+		}
+		results = append(results, port.CopiedMessage{SourceUID: uid, DestUID: destUID})
+	}
+	return results, nil
+}
+
+func (s *MailStore) copyOne(ctx context.Context, sourceFolderID string, sourceUID uint32, destFolderID string) (uint32, error) {
+	tx, err := s.pool.Begin(ctx)
+	if err != nil {
+		return 0, fmt.Errorf("begin transaction: %w", err)
+	}
+	defer tx.Rollback(ctx)
+
+	if err := lockFolders(ctx, tx, destFolderID); err != nil {
+		return 0, err
+	}
+	src, err := loadMessage(ctx, tx, sourceFolderID, sourceUID)
+	if err != nil {
+		return 0, err
+	}
+
+	var destUID int64
+	var destMailboxID string
+	if err := tx.QueryRow(ctx, `SELECT uid_next, mailbox_id::text FROM folders WHERE id = $1`, destFolderID).Scan(&destUID, &destMailboxID); err != nil {
+		return 0, fmt.Errorf("read destination folder: %w", err)
+	}
+
+	unread := 0
+	if !src.Seen {
+		unread = 1
+	}
+	var modseq int64
+	if err := tx.QueryRow(ctx, `
+		UPDATE folders
+		   SET uid_next = uid_next + 1, highest_modseq = highest_modseq + 1,
+		       total_count = total_count + 1, unread_count = unread_count + $2
+		 WHERE id = $1
+		RETURNING highest_modseq`, destFolderID, unread).Scan(&modseq); err != nil {
+		return 0, fmt.Errorf("advance destination folder: %w", err)
+	}
+
+	var newID uuid.UUID
+	var newReceivedAt any
+	if err := tx.QueryRow(ctx, `
+		INSERT INTO email_messages (
+			mailbox_id, folder_id, uid, modseq, blob_id,
+			sender_address, recipient_addresses, size_bytes,
+			spf_result, dkim_result, dmarc_result,
+			from_display_name, subject, snippet, message_id_header, in_reply_to, thread_id, has_attachments,
+			arc_result, dane_status, tls_version, spam_score, spam_verdict, virus_name
+		)
+		SELECT $2::uuid, $3::uuid, $4::bigint, $5::bigint, blob_id,
+			sender_address, recipient_addresses, size_bytes,
+			spf_result, dkim_result, dmarc_result,
+			from_display_name, subject, snippet, message_id_header, in_reply_to, thread_id, has_attachments,
+			arc_result, dane_status, tls_version, spam_score, spam_verdict, virus_name
+		  FROM email_messages WHERE id = $1 AND received_at = $6
+		RETURNING id, received_at`,
+		src.ID, destMailboxID, destFolderID, destUID, modseq, src.ReceivedAt).Scan(&newID, &newReceivedAt); err != nil {
+		return 0, fmt.Errorf("insert copied message: %w", err)
+	}
+
+	if _, err := tx.Exec(ctx, `UPDATE message_blobs SET ref_count = ref_count + 1 WHERE id = (SELECT blob_id FROM email_messages WHERE id = $1 AND received_at = $2)`,
+		newID, newReceivedAt); err != nil {
+		return 0, fmt.Errorf("share the blob: %w", err)
+	}
+	if _, err := tx.Exec(ctx, `UPDATE mailboxes SET used_bytes = used_bytes + $1 WHERE id = $2`, src.Size, destMailboxID); err != nil {
+		return 0, fmt.Errorf("count the copy against the quota: %w", err)
+	}
+	if _, err := tx.Exec(ctx, `
+		INSERT INTO message_flags (message_id, received_at, flag)
+		SELECT $1, $2, flag FROM message_flags WHERE message_id = $3 AND received_at = $4`,
+		newID, newReceivedAt, src.ID, src.ReceivedAt); err != nil {
+		return 0, fmt.Errorf("copy flags: %w", err)
+	}
+
+	return uint32(destUID), tx.Commit(ctx)
+}
+
+// DeleteFolder removes a folder the user made, with the mail in it. The
+// messages are expunged rather than deleted (recoverable, like any expunge) and
+// their bytes go back to the quota.
+func (s *MailStore) DeleteFolder(ctx context.Context, folderID string) error {
+	tx, err := s.pool.Begin(ctx)
+	if err != nil {
+		return err
+	}
+	defer tx.Rollback(ctx)
+
+	var mailboxID string
+	if err := tx.QueryRow(ctx, `SELECT mailbox_id::text FROM folders WHERE id = $1 FOR UPDATE`, folderID).Scan(&mailboxID); err != nil {
+		return fmt.Errorf("lock folder: %w", err)
+	}
+
+	var freed int64
+	if err := tx.QueryRow(ctx, `
+		WITH gone AS (
+			UPDATE email_messages SET expunged_at = NOW()
+			 WHERE folder_id = $1 AND expunged_at IS NULL
+			RETURNING size_bytes)
+		SELECT COALESCE(SUM(size_bytes), 0) FROM gone`, folderID).Scan(&freed); err != nil {
+		return fmt.Errorf("expunge the folder's messages: %w", err)
+	}
+
+	if _, err := tx.Exec(ctx, `UPDATE mailboxes SET used_bytes = GREATEST(0, used_bytes - $1) WHERE id = $2`, freed, mailboxID); err != nil {
+		return fmt.Errorf("give quota back: %w", err)
+	}
+	if _, err := tx.Exec(ctx, `DELETE FROM folders WHERE id = $1`, folderID); err != nil {
+		return fmt.Errorf("delete folder: %w", err)
+	}
+	return tx.Commit(ctx)
+}
diff --git a/services/protocols/internal/infrastructure/postgres/mail_store_read.go b/services/protocols/internal/infrastructure/postgres/mail_store_read.go
new file mode 100644
index 0000000..7b53943
--- /dev/null
+++ b/services/protocols/internal/infrastructure/postgres/mail_store_read.go
@@ -0,0 +1,202 @@
+package postgres
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"time"
+
+	"github.com/google/uuid"
+	"github.com/jackc/pgx/v5"
+)
+
+// The read side of MailStore.
+//
+// IMAP (LIST, SELECT, FETCH) and the webmail (folder list, message list) used to
+// read the same tables with different queries, and so could answer differently:
+// IMAP took a folder's message count from a cached column, the webmail counted
+// the rows. A client comparing the two saw numbers that disagreed. They now ask
+// the same question, and the answer is derived from the messages themselves, so
+// a folder can only ever report what is actually in it.
+
+// FolderInfo is one folder with the numbers a client needs.
+type FolderInfo struct {
+	ID            string
+	Name          string
+	SpecialUse    string
+	UIDNext       int64
+	UIDValidity   int64
+	HighestModSeq int64
+	// Total and Unread are counted from the messages, not read from the cached
+	// columns: the columns are kept true by every write path, and counting here
+	// makes a wrong one visible instead of repeated.
+	Total  int
+	Unread int
+}
+
+const folderColumns = `
+	SELECT f.id::text, f.name, COALESCE(f.special_use, ''),
+	       f.uid_next, f.uid_validity, f.highest_modseq,
+	       COUNT(e.id)::int,
+	       COUNT(e.id) FILTER (
+	         WHERE NOT EXISTS (SELECT 1 FROM message_flags mf
+	                            WHERE mf.message_id = e.id
+	                              AND mf.received_at = e.received_at
+	                              AND mf.flag = '\Seen')
+	       )::int
+	  FROM folders f
+	  LEFT JOIN email_messages e ON e.folder_id = f.id AND e.expunged_at IS NULL`
+
+func scanFolder(row pgx.Row) (FolderInfo, error) {
+	var f FolderInfo
+	err := row.Scan(&f.ID, &f.Name, &f.SpecialUse, &f.UIDNext, &f.UIDValidity, &f.HighestModSeq, &f.Total, &f.Unread)
+	return f, err
+}
+
+// Folders lists a mailbox's folders by name.
+func (s *MailStore) Folders(ctx context.Context, mailboxID string) ([]FolderInfo, error) {
+	rows, err := s.pool.Query(ctx, folderColumns+`
+	 WHERE f.mailbox_id = $1
+	 GROUP BY f.id
+	 ORDER BY f.name`, mailboxID)
+	if err != nil {
+		return nil, fmt.Errorf("list folders: %w", err)
+	}
+	defer rows.Close()
+
+	var out []FolderInfo
+	for rows.Next() {
+		f, err := scanFolder(rows)
+		if err != nil {
+			return nil, err
+		}
+		out = append(out, f)
+	}
+	return out, rows.Err()
+}
+
+// FolderByName finds one folder by its exact name; nil, nil when there is none
+// (IMAP SELECT treats that as a normal answer, not a failure).
+func (s *MailStore) FolderByName(ctx context.Context, mailboxID, name string) (*FolderInfo, error) {
+	f, err := scanFolder(s.pool.QueryRow(ctx, folderColumns+`
+	 WHERE f.mailbox_id = $1 AND f.name = $2
+	 GROUP BY f.id`, mailboxID, name))
+	if errors.Is(err, pgx.ErrNoRows) {
+		return nil, nil
+	}
+	if err != nil {
+		return nil, err
+	}
+	return &f, nil
+}
+
+// MessageInfo is one message as either a mail client or the webmail lists it.
+type MessageInfo struct {
+	UID            uint32
+	BlobID         uuid.UUID
+	Size           int64
+	ReceivedAt     time.Time
+	ModSeq         uint64
+	Flags          []string
+	Subject        string
+	SenderAddress  string
+	FromName       string
+	Snippet        string
+	HasAttachments bool
+	SpamVerdict    string
+	DmarcResult    string
+}
+
+// HasFlag reports whether the message carries the flag.
+func (m MessageInfo) HasFlag(flag string) bool {
+	for _, f := range m.Flags {
+		if f == flag {
+			return true
+		}
+	}
+	return false
+}
+
+// MessageQuery shapes a listing. The zero value lists every message of the
+// folder by UID ascending, which is what IMAP needs to number them.
+type MessageQuery struct {
+	// NewestFirst orders by arrival, newest first, as the webmail shows them
+	NewestFirst bool
+	// Search keeps messages whose subject, sender or snippet contains it
+	Search string
+	// Limit and Offset page the result; Limit 0 means no limit
+	Limit  int
+	Offset int
+}
+
+// Messages lists a folder's live messages with their flags.
+func (s *MailStore) Messages(ctx context.Context, folderID string, q MessageQuery) ([]MessageInfo, error) {
+	order := `e.uid ASC`
+	if q.NewestFirst {
+		order = `e.received_at DESC, e.uid DESC`
+	}
+	limit := q.Limit
+	if limit <= 0 {
+		limit = 1<<31 - 1
+	}
+	offset := q.Offset
+	if offset < 0 {
+		offset = 0
+	}
+
+	rows, err := s.pool.Query(ctx, `
+		SELECT e.uid, e.blob_id, e.size_bytes, e.received_at, e.modseq,
+		       COALESCE((SELECT array_agg(mf.flag) FROM message_flags mf
+		                  WHERE mf.message_id = e.id AND mf.received_at = e.received_at), '{}'),
+		       COALESCE(e.subject, ''), e.sender_address::text,
+		       COALESCE(e.from_display_name, ''), COALESCE(e.snippet, ''),
+		       e.has_attachments, COALESCE(e.spam_verdict, ''), COALESCE(e.dmarc_result, '')
+		  FROM email_messages e
+		 WHERE e.folder_id = $1 AND e.expunged_at IS NULL
+		   AND ($2 = '' OR e.subject ILIKE '%' || $2 || '%'
+		                OR e.sender_address::text ILIKE '%' || $2 || '%'
+		                OR e.snippet ILIKE '%' || $2 || '%')
+		 ORDER BY `+order+`
+		 LIMIT $3 OFFSET $4`, folderID, q.Search, limit, offset)
+	if err != nil {
+		return nil, fmt.Errorf("list messages: %w", err)
+	}
+	defer rows.Close()
+
+	var out []MessageInfo
+	for rows.Next() {
+		var m MessageInfo
+		if err := rows.Scan(&m.UID, &m.BlobID, &m.Size, &m.ReceivedAt, &m.ModSeq, &m.Flags,
+			&m.Subject, &m.SenderAddress, &m.FromName, &m.Snippet,
+			&m.HasAttachments, &m.SpamVerdict, &m.DmarcResult); err != nil {
+			return nil, err
+		}
+		out = append(out, m)
+	}
+	return out, rows.Err()
+}
+
+// MessageBlob resolves one message to its stored blob, or ErrMessageNotFound.
+func (s *MailStore) MessageBlob(ctx context.Context, folderID string, uid uint32) (uuid.UUID, error) {
+	var blobID uuid.UUID
+	err := s.pool.QueryRow(ctx, `
+		SELECT blob_id FROM email_messages WHERE folder_id = $1 AND uid = $2 AND expunged_at IS NULL`,
+		folderID, int64(uid)).Scan(&blobID)
+	if errors.Is(err, pgx.ErrNoRows) {
+		return uuid.Nil, ErrMessageNotFound
+	}
+	return blobID, err
+}
+
+// MailboxIDByAddress resolves an active address to its mailbox id.
+func (s *MailStore) MailboxIDByAddress(ctx context.Context, address string) (string, error) {
+	var id string
+	err := s.pool.QueryRow(ctx, `
+		SELECT m.id::text FROM mailboxes m
+		  JOIN domains d ON d.id = m.domain_id
+		 WHERE m.email_address = $1 AND m.is_active AND d.is_active`, address).Scan(&id)
+	if errors.Is(err, pgx.ErrNoRows) {
+		return "", ErrMessageNotFound
+	}
+	return id, err
+}
diff --git a/services/protocols/internal/infrastructure/postgres/mailbox_state_migration_test.go b/services/protocols/internal/infrastructure/postgres/mailbox_state_migration_test.go
new file mode 100644
index 0000000..81be194
--- /dev/null
+++ b/services/protocols/internal/infrastructure/postgres/mailbox_state_migration_test.go
@@ -0,0 +1,158 @@
+package postgres
+
+import (
+	"context"
+	"os"
+	"testing"
+
+	"github.com/google/uuid"
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+// runMigration0014 applies the migration file itself, so the test cannot drift
+// from what production runs. It is idempotent by design, which is also tested.
+func runMigration0014(t *testing.T, pool *pgxpool.Pool) {
+	t.Helper()
+	sql, err := os.ReadFile("../../../../../migrations/0014_mailbox_state_single_source.up.sql")
+	if err != nil {
+		t.Fatalf("read migration: %v", err)
+	}
+	if _, err := pool.Exec(context.Background(), string(sql)); err != nil {
+		t.Fatalf("apply migration 0014: %v", err)
+	}
+}
+
+func folderNames(t *testing.T, pool *pgxpool.Pool, mailboxID string) map[string]string {
+	t.Helper()
+	rows, err := pool.Query(context.Background(), `SELECT name, COALESCE(special_use, '') FROM folders WHERE mailbox_id = $1`, mailboxID)
+	if err != nil {
+		t.Fatalf("list folders: %v", err)
+	}
+	defer rows.Close()
+	out := map[string]string{}
+	for rows.Next() {
+		var name, role string
+		if err := rows.Scan(&name, &role); err != nil {
+			t.Fatalf("scan: %v", err)
+		}
+		out[name] = role
+	}
+	return out
+}
+
+// Numbers that two paths left wrong are corrected from the rows.
+func TestMigration0014_ReconcilesDriftedCountersAndQuota(t *testing.T) {
+	pool := testPool(t)
+	ctx := context.Background()
+	mailboxID := seedMailbox(t, pool)
+	deliver(t, pool, mailboxID, "INBOX", "a", false)
+	deliver(t, pool, mailboxID, "INBOX", "b", true)
+	deliver(t, pool, mailboxID, "Sent", "c", true)
+
+	// The drift as it was found: counters and quota that disagree with the rows
+	if _, err := pool.Exec(ctx, `UPDATE folders SET unread_count = 9, total_count = 7 WHERE mailbox_id = $1`, mailboxID); err != nil {
+		t.Fatalf("corrupt counters: %v", err)
+	}
+	if _, err := pool.Exec(ctx, `UPDATE mailboxes SET used_bytes = 12345 WHERE id = $1`, mailboxID); err != nil {
+		t.Fatalf("corrupt quota: %v", err)
+	}
+
+	runMigration0014(t, pool)
+	assertConsistent(t, pool, mailboxID, "the reconciliation")
+
+	runMigration0014(t, pool)
+	assertConsistent(t, pool, mailboxID, "running the reconciliation a second time")
+}
+
+// A mailbox that is already right is left exactly as it was.
+func TestMigration0014_LeavesATrueMailboxAlone(t *testing.T) {
+	pool := testPool(t)
+	ctx := context.Background()
+	mailboxID := seedMailbox(t, pool)
+	deliver(t, pool, mailboxID, "INBOX", "a", false)
+	before, usedBefore, _ := mailState(t, pool, mailboxID)
+
+	runMigration0014(t, pool)
+
+	after, usedAfter, _ := mailState(t, pool, mailboxID)
+	for name, f := range before {
+		if after[name].CachedTotal != f.CachedTotal || after[name].CachedUnread != f.CachedUnread || after[name].HighestModSeq != f.HighestModSeq {
+			t.Errorf("%s changed: %+v -> %+v", name, f, after[name])
+		}
+	}
+	if usedAfter != usedBefore {
+		t.Errorf("used_bytes changed from %d to %d", usedBefore, usedAfter)
+	}
+	_ = ctx
+}
+
+// The one list of standard folders: what is missing is added, what is there is
+// not duplicated, and running it again changes nothing.
+func TestProvisionDefaultFolders(t *testing.T) {
+	pool := testPool(t)
+	ctx := context.Background()
+	runMigration0014(t, pool)
+
+	domainID, mailboxID := uuid.New(), uuid.New()
+	name := "prov" + uuid.NewString()[:8] + ".test"
+	if _, err := pool.Exec(ctx, `INSERT INTO domains (id, name, punycode_name, is_active) VALUES ($1,$2,$3,true)`, domainID, name, name); err != nil {
+		t.Fatalf("seed domain: %v", err)
+	}
+	t.Cleanup(func() { _, _ = pool.Exec(context.Background(), `DELETE FROM domains WHERE id = $1`, domainID) })
+	if _, err := pool.Exec(ctx, `INSERT INTO mailboxes (id, domain_id, local_part, email_address, password_hash, is_active) VALUES ($1,$2,'u',$3,'x',true)`,
+		mailboxID, domainID, "u@"+name); err != nil {
+		t.Fatalf("seed mailbox: %v", err)
+	}
+
+	want := map[string]string{"INBOX": "inbox", "Sent": "sent", "Drafts": "drafts", "Trash": "trash", "Junk": "junk", "Archive": "archive", "Reports": ""}
+
+	if _, err := pool.Exec(ctx, `SELECT provision_default_folders($1)`, mailboxID); err != nil {
+		t.Fatalf("provision: %v", err)
+	}
+	got := folderNames(t, pool, mailboxID.String())
+	for n, role := range want {
+		if r, ok := got[n]; !ok || r != role {
+			t.Errorf("folder %q: present=%v role=%q, want role %q", n, ok, r, role)
+		}
+	}
+	if len(got) != len(want) {
+		t.Errorf("got %d folders, want %d: %v", len(got), len(want), got)
+	}
+
+	if _, err := pool.Exec(ctx, `SELECT provision_default_folders($1)`, mailboxID); err != nil {
+		t.Fatalf("provision again: %v", err)
+	}
+	if again := folderNames(t, pool, mailboxID.String()); len(again) != len(want) {
+		t.Errorf("a second call changed the folder count to %d", len(again))
+	}
+}
+
+// A folder that exists under another capitalisation counts as present, and the
+// folder keeps the owner's mail.
+func TestProvisionDefaultFolders_DoesNotDuplicateByCase(t *testing.T) {
+	pool := testPool(t)
+	ctx := context.Background()
+	runMigration0014(t, pool)
+	mailboxID := seedMailbox(t, pool) // INBOX, Sent, Drafts, Trash
+
+	if _, err := pool.Exec(ctx, `INSERT INTO folders (mailbox_id, name, special_use) VALUES ($1, 'reports', NULL)`, mailboxID); err != nil {
+		t.Fatalf("seed: %v", err)
+	}
+	if _, err := pool.Exec(ctx, `SELECT provision_default_folders($1)`, mailboxID); err != nil {
+		t.Fatalf("provision: %v", err)
+	}
+
+	got := folderNames(t, pool, mailboxID)
+	reports := 0
+	for n := range got {
+		if n == "reports" || n == "Reports" {
+			reports++
+		}
+	}
+	if reports != 1 {
+		t.Errorf("found %d reports folders, want 1: %v", reports, got)
+	}
+	if len(got) != 7 {
+		t.Errorf("got %d folders, want 7: %v", len(got), got)
+	}
+}
diff --git a/services/protocols/internal/infrastructure/postgres/message_query_repository.go b/services/protocols/internal/infrastructure/postgres/message_query_repository.go
index 09a0c0c..9f647ef 100644
--- a/services/protocols/internal/infrastructure/postgres/message_query_repository.go
+++ b/services/protocols/internal/infrastructure/postgres/message_query_repository.go
@@ -8,37 +8,26 @@ import (
 	"lambdamail/protocols/internal/application/port"
 )
 
-// MessageQueryRepository implements port.MessageQueryRepository against Postgres.
+// MessageQueryRepository lists a folder's messages for IMAP FETCH, through the
+// same MailStore listing the webmail uses.
 type MessageQueryRepository struct {
-	pool *pgxpool.Pool
+	store *MailStore
 }
 
 func NewMessageQueryRepository(pool *pgxpool.Pool) *MessageQueryRepository {
-	return &MessageQueryRepository{pool: pool}
+	return &MessageQueryRepository{store: NewMailStore(pool)}
 }
 
 func (r *MessageQueryRepository) ListMessages(ctx context.Context, folderID string) ([]port.MessageRecord, error) {
-	rows, err := r.pool.Query(ctx, `
-		SELECT m.uid, m.blob_id, m.size_bytes, m.received_at, m.modseq,
-		       COALESCE(array_agg(f.flag) FILTER (WHERE f.flag IS NOT NULL), '{}')
-		FROM email_messages m
-		LEFT JOIN message_flags f ON f.message_id = m.id AND f.received_at = m.received_at
-		WHERE m.folder_id = $1 AND m.expunged_at IS NULL
-		GROUP BY m.uid, m.blob_id, m.size_bytes, m.received_at, m.modseq
-		ORDER BY m.uid ASC
-	`, folderID)
+	messages, err := r.store.Messages(ctx, folderID, MessageQuery{})
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
-
 	var out []port.MessageRecord
-	for rows.Next() {
-		var rec port.MessageRecord
-		if err := rows.Scan(&rec.UID, &rec.BlobID, &rec.SizeBytes, &rec.ReceivedAt, &rec.ModSeq, &rec.Flags); err != nil {
-			return nil, err
-		}
-		out = append(out, rec)
+	for _, m := range messages {
+		out = append(out, port.MessageRecord{
+			UID: m.UID, BlobID: m.BlobID, SizeBytes: m.Size, ReceivedAt: m.ReceivedAt, Flags: m.Flags, ModSeq: m.ModSeq,
+		})
 	}
-	return out, rows.Err()
+	return out, nil
 }
diff --git a/services/protocols/internal/infrastructure/postgres/webmail_repository.go b/services/protocols/internal/infrastructure/postgres/webmail_repository.go
index f39c8ca..bd1521f 100644
--- a/services/protocols/internal/infrastructure/postgres/webmail_repository.go
+++ b/services/protocols/internal/infrastructure/postgres/webmail_repository.go
@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"sort"
 
 	"github.com/google/uuid"
 	"github.com/jackc/pgx/v5"
@@ -19,456 +20,182 @@ var ErrMessageNotFound = errors.New("webmail: message not found")
 
 // WebmailRepository implements the webmail read side against Postgres.
 type WebmailRepository struct {
-	pool *pgxpool.Pool
+	pool  *pgxpool.Pool
+	store *MailStore
 }
 
 func NewWebmailRepository(pool *pgxpool.Pool) *WebmailRepository {
-	return &WebmailRepository{pool: pool}
+	return &WebmailRepository{pool: pool, store: NewMailStore(pool)}
 }
 
+// The methods below only read. They do not query on their own: the webmail asks
+// MailStore the same questions IMAP does and shapes the answers for the
+// browser, so a folder shows the same numbers in both.
+
 func (r *WebmailRepository) FindMailboxIDByAddress(ctx context.Context, address string) (string, error) {
-	var id string
-	err := r.pool.QueryRow(ctx, `
-		SELECT m.id::text FROM mailboxes m
-		  JOIN domains d ON d.id = m.domain_id
-		 WHERE m.email_address = $1 AND m.is_active AND d.is_active
-	`, address).Scan(&id)
-	if errors.Is(err, pgx.ErrNoRows) {
-		return "", ErrMessageNotFound
-	}
-	return id, err
+	return r.store.MailboxIDByAddress(ctx, address)
 }
 
+// roleOrder is how the folder list is arranged for people: the folders they use
+// every day first, in a fixed order, then their own by name.
+var roleOrder = map[string]int{"inbox": 0, "drafts": 1, "sent": 2, "archive": 3, "junk": 4, "trash": 5}
+
 func (r *WebmailRepository) ListFolders(ctx context.Context, mailboxID string) ([]port.WebmailFolder, error) {
-	// The counts are derived from the messages themselves rather than read out
-	// of folders.unread_count/total_count.
-	//
-	// Those columns are a denormalised cache maintained by every write path,
-	// and once any one of them was wrong nothing brought it back: the number
-	// the user saw stayed wrong through a reload, a logout and a fresh login,
-	// because the wrongness was stored. Deriving here is authoritative and
-	// self-healing - a folder can only ever report what is actually in it.
-	//
-	// The columns stay maintained for IMAP's sake (STATUS answers from them),
-	// so this is a correction at the read side, not their removal.
-	rows, err := r.pool.Query(ctx, `
-		SELECT f.id::text, f.name, COALESCE(f.special_use, ''),
-		       COUNT(e.id) FILTER (
-		         WHERE NOT EXISTS (SELECT 1 FROM message_flags mf
-		                            WHERE mf.message_id = e.id
-		                              AND mf.received_at = e.received_at
-		                              AND mf.flag = '\Seen')
-		       )::int AS unread_count,
-		       COUNT(e.id)::int AS total_count
-		  FROM folders f
-		  LEFT JOIN email_messages e
-		         ON e.folder_id = f.id AND e.expunged_at IS NULL
-		 WHERE f.mailbox_id = $1
-		 GROUP BY f.id, f.name, f.special_use
-		 ORDER BY CASE f.special_use
-		            WHEN 'inbox' THEN 0 WHEN 'drafts' THEN 1 WHEN 'sent' THEN 2
-		            WHEN 'archive' THEN 3 WHEN 'junk' THEN 4 WHEN 'trash' THEN 5
-		            ELSE 6 END, f.name
-	`, mailboxID)
+	folders, err := r.store.Folders(ctx, mailboxID)
 	if err != nil {
-		return nil, fmt.Errorf("list folders: %w", err)
+		return nil, err
 	}
-	defer rows.Close()
 
-	folders := []port.WebmailFolder{}
-	for rows.Next() {
-		var f port.WebmailFolder
-		if err := rows.Scan(&f.ID, &f.Name, &f.SpecialUse, &f.UnreadCount, &f.TotalCount); err != nil {
-			return nil, err
+	out := make([]port.WebmailFolder, 0, len(folders))
+	for _, f := range folders {
+		out = append(out, port.WebmailFolder{ID: f.ID, Name: f.Name, SpecialUse: f.SpecialUse, UnreadCount: f.Unread, TotalCount: f.Total})
+	}
+
+	rank := func(f port.WebmailFolder) int {
+		if n, ok := roleOrder[f.SpecialUse]; ok {
+			return n
 		}
-		folders = append(folders, f)
+		return 6
 	}
-	return folders, rows.Err()
+	sort.SliceStable(out, func(i, j int) bool {
+		if ri, rj := rank(out[i]), rank(out[j]); ri != rj {
+			return ri < rj
+		}
+		return out[i].Name < out[j].Name
+	})
+	return out, nil
 }
 
-// folderCondition matches either the special-use role ("inbox") or the literal
-// folder name, so the UI can address a folder the same way IMAP does.
-const folderCondition = `(f.special_use = LOWER($2) OR LOWER(f.name) = LOWER($2))`
-
 func (r *WebmailRepository) ListMessages(
 	ctx context.Context, mailboxID, folderName, search string, limit, offset int,
 ) ([]port.WebmailMessage, error) {
 	if limit <= 0 || limit > 200 {
 		limit = 50
 	}
-	if offset < 0 {
-		offset = 0
-	}
 
-	rows, err := r.pool.Query(ctx, `
-		SELECT e.uid, COALESCE(e.subject, ''), e.sender_address::text,
-		       COALESCE(e.from_display_name, ''), COALESCE(e.snippet, ''),
-		       e.size_bytes, e.received_at, e.has_attachments,
-		       EXISTS (SELECT 1 FROM message_flags mf
-		                WHERE mf.message_id = e.id AND mf.received_at = e.received_at AND mf.flag = '\Seen'),
-		       EXISTS (SELECT 1 FROM message_flags mf
-		                WHERE mf.message_id = e.id AND mf.received_at = e.received_at AND mf.flag = '\Flagged'),
-		       EXISTS (SELECT 1 FROM message_flags mf
-		                WHERE mf.message_id = e.id AND mf.received_at = e.received_at AND mf.flag = '\Answered'),
-		       COALESCE(e.spam_verdict, ''), COALESCE(e.dmarc_result, '')
-		  FROM email_messages e
-		  JOIN folders f ON f.id = e.folder_id
-		 WHERE e.mailbox_id = $1 AND `+folderCondition+`
-		   AND e.expunged_at IS NULL
-		   AND ($3 = '' OR e.subject ILIKE '%%' || $3 || '%%'
-		                OR e.sender_address::text ILIKE '%%' || $3 || '%%'
-		                OR e.snippet ILIKE '%%' || $3 || '%%')
-		 ORDER BY e.received_at DESC, e.uid DESC
-		 LIMIT $4 OFFSET $5
-	`, mailboxID, folderName, search, limit, offset)
+	folderID, err := r.store.ResolveFolder(ctx, mailboxID, folderName)
+	if errors.Is(err, port.ErrFolderMissing) {
+		return []port.WebmailMessage{}, nil
+	}
 	if err != nil {
-		return nil, fmt.Errorf("list messages: %w", err)
+		return nil, err
 	}
-	defer rows.Close()
 
-	messages := []port.WebmailMessage{}
-	for rows.Next() {
-		var m port.WebmailMessage
-		if err := rows.Scan(
-			&m.UID, &m.Subject, &m.SenderAddress, &m.FromName, &m.Snippet,
-			&m.SizeBytes, &m.ReceivedAt, &m.HasAttachments,
-			&m.Seen, &m.Flagged, &m.Answered, &m.SpamVerdict, &m.DmarcResult,
-		); err != nil {
-			return nil, err
-		}
-		messages = append(messages, m)
+	messages, err := r.store.Messages(ctx, folderID, MessageQuery{NewestFirst: true, Search: search, Limit: limit, Offset: offset})
+	if err != nil {
+		return nil, err
 	}
-	return messages, rows.Err()
+
+	out := make([]port.WebmailMessage, 0, len(messages))
+	for _, m := range messages {
+		out = append(out, port.WebmailMessage{
+			UID: m.UID, Subject: m.Subject, SenderAddress: m.SenderAddress, FromName: m.FromName, Snippet: m.Snippet,
+			SizeBytes: m.Size, ReceivedAt: m.ReceivedAt, HasAttachments: m.HasAttachments,
+			Seen: m.HasFlag(`\Seen`), Flagged: m.HasFlag(`\Flagged`), Answered: m.HasFlag(`\Answered`),
+			SpamVerdict: m.SpamVerdict, DmarcResult: m.DmarcResult,
+		})
+	}
+	return out, nil
 }
 
-func (r *WebmailRepository) GetMessageBlob(
-	ctx context.Context, mailboxID, folderName string, uid uint32,
-) (uuid.UUID, error) {
-	var blobID uuid.UUID
-	err := r.pool.QueryRow(ctx, `
-		SELECT e.blob_id FROM email_messages e
-		  JOIN folders f ON f.id = e.folder_id
-		 WHERE e.mailbox_id = $1 AND `+folderCondition+`
-		   AND e.uid = $3 AND e.expunged_at IS NULL
-	`, mailboxID, folderName, int64(uid)).Scan(&blobID)
-	if errors.Is(err, pgx.ErrNoRows) {
-		return uuid.Nil, ErrMessageNotFound
+func (r *WebmailRepository) GetMessageBlob(ctx context.Context, mailboxID, folderName string, uid uint32) (uuid.UUID, error) {
+	folderID, err := r.messageFolder(ctx, mailboxID, folderName)
+	if err != nil {
+		return uuid.Nil, err
 	}
-	return blobID, err
+	return r.store.MessageBlob(ctx, folderID, uid)
 }
 
-// MarkSeen keeps the \Seen flag and the folder's unread counter in step. They
-// are updated together in one transaction, because a counter that disagrees
-// with the flags is what makes an inbox show unread mail that is not there.
-func (r *WebmailRepository) MarkSeen(
-	ctx context.Context, mailboxID, folderName string, uid uint32, seen bool,
-) error {
-	tx, err := r.pool.Begin(ctx)
+// The methods below change state. They do not do it themselves: the webmail
+// names a message by mailbox, folder name and UID, MailStore by folder id and
+// UID, and these translate. Every counter, modseq and quota rule lives in
+// MailStore, which IMAP uses too, so the two can no longer disagree.
+
+// messageFolder resolves the folder a message is addressed in. A folder that is
+// not there and a message that is not there look the same to the caller, so a
+// stranger cannot probe which folders exist.
+func (r *WebmailRepository) messageFolder(ctx context.Context, mailboxID, folderName string) (string, error) {
+	id, err := r.store.ResolveFolder(ctx, mailboxID, folderName)
+	if errors.Is(err, port.ErrFolderMissing) {
+		return "", ErrMessageNotFound
+	}
+	return id, err
+}
+
+// MarkSeen sets or clears \Seen. The unread counter follows inside MailStore.
+func (r *WebmailRepository) MarkSeen(ctx context.Context, mailboxID, folderName string, uid uint32, seen bool) error {
+	return r.setFlag(ctx, mailboxID, folderName, uid, `\Seen`, seen)
+}
+
+// MarkFlagged sets or clears \Flagged.
+func (r *WebmailRepository) MarkFlagged(ctx context.Context, mailboxID, folderName string, uid uint32, flagged bool) error {
+	return r.setFlag(ctx, mailboxID, folderName, uid, `\Flagged`, flagged)
+}
+
+func (r *WebmailRepository) setFlag(ctx context.Context, mailboxID, folderName string, uid uint32, flag string, on bool) error {
+	folderID, err := r.messageFolder(ctx, mailboxID, folderName)
 	if err != nil {
 		return err
 	}
-	defer tx.Rollback(ctx)
+	op := port.FlagOpAdd
+	if !on {
+		op = port.FlagOpDel
+	}
+	_, err = r.store.SetFlags(ctx, folderID, uid, op, []string{flag}, 0)
+	return err
+}
 
-	var messageID uuid.UUID
-	var receivedAt any
-	var folderID string
-	err = tx.QueryRow(ctx, `
-		SELECT e.id, e.received_at, f.id::text FROM email_messages e
-		  JOIN folders f ON f.id = e.folder_id
-		 WHERE e.mailbox_id = $1 AND `+folderCondition+`
-		   AND e.uid = $3 AND e.expunged_at IS NULL
-	`, mailboxID, folderName, int64(uid)).Scan(&messageID, &receivedAt, &folderID)
-	if errors.Is(err, pgx.ErrNoRows) {
+// Expunge removes one message for good (soft delete) and gives its bytes back.
+func (r *WebmailRepository) Expunge(ctx context.Context, mailboxID, folderName string, uid uint32) error {
+	folderID, err := r.messageFolder(ctx, mailboxID, folderName)
+	if err != nil {
+		return err
+	}
+	removed, err := r.store.Expunge(ctx, folderID, []uint32{uid})
+	if err != nil {
+		return err
+	}
+	if removed == 0 {
 		return ErrMessageNotFound
 	}
-	if err != nil {
-		return err
-	}
-
-	var changed int64
-	if seen {
-		tag, err := tx.Exec(ctx, `
-			INSERT INTO message_flags (message_id, received_at, flag)
-			VALUES ($1, $2, '\Seen') ON CONFLICT DO NOTHING
-		`, messageID, receivedAt)
-		if err != nil {
-			return err
-		}
-		changed = tag.RowsAffected()
-	} else {
-		tag, err := tx.Exec(ctx, `
-			DELETE FROM message_flags WHERE message_id = $1 AND received_at = $2 AND flag = '\Seen'
-		`, messageID, receivedAt)
-		if err != nil {
-			return err
-		}
-		changed = tag.RowsAffected()
-	}
-
-	// Only a real transition moves the counter, so opening an already-read
-	// message repeatedly cannot drive unread_count negative.
-	if changed > 0 {
-		delta := 1
-		if seen {
-			delta = -1
-		}
-		if _, err := tx.Exec(ctx, `
-			UPDATE folders SET unread_count = GREATEST(0, unread_count + $2), highest_modseq = highest_modseq + 1
-			 WHERE id = $1
-		`, folderID, delta); err != nil {
-			return err
-		}
-	}
-
-	return tx.Commit(ctx)
-}
-
-// MarkFlagged sets or clears \Flagged. Unlike \Seen it moves no counter, but a
-// real change still bumps the folder's modseq: that is how an IMAP client
-// holding the folder open learns the flag changed without a full resync.
-func (r *WebmailRepository) MarkFlagged(
-	ctx context.Context, mailboxID, folderName string, uid uint32, flagged bool,
-) error {
-	tx, err := r.pool.Begin(ctx)
-	if err != nil {
-		return err
-	}
-	defer tx.Rollback(ctx)
-
-	var messageID uuid.UUID
-	var receivedAt any
-	var folderID string
-	err = tx.QueryRow(ctx, `
-		SELECT e.id, e.received_at, f.id::text FROM email_messages e
-		  JOIN folders f ON f.id = e.folder_id
-		 WHERE e.mailbox_id = $1 AND `+folderCondition+`
-		   AND e.uid = $3 AND e.expunged_at IS NULL
-	`, mailboxID, folderName, int64(uid)).Scan(&messageID, &receivedAt, &folderID)
-	if errors.Is(err, pgx.ErrNoRows) {
-		return ErrMessageNotFound
-	}
-	if err != nil {
-		return err
-	}
-
-	var changed int64
-	if flagged {
-		tag, err := tx.Exec(ctx, `
-			INSERT INTO message_flags (message_id, received_at, flag)
-			VALUES ($1, $2, '\Flagged') ON CONFLICT DO NOTHING
-		`, messageID, receivedAt)
-		if err != nil {
-			return err
-		}
-		changed = tag.RowsAffected()
-	} else {
-		tag, err := tx.Exec(ctx, `
-			DELETE FROM message_flags WHERE message_id = $1 AND received_at = $2 AND flag = '\Flagged'
-		`, messageID, receivedAt)
-		if err != nil {
-			return err
-		}
-		changed = tag.RowsAffected()
-	}
-
-	if changed > 0 {
-		if _, err := tx.Exec(ctx,
-			`UPDATE folders SET highest_modseq = highest_modseq + 1 WHERE id = $1`, folderID); err != nil {
-			return err
-		}
-	}
-	return tx.Commit(ctx)
-}
-
-// Expunge marks one message deleted and keeps the folder counters in step.
-//
-// Soft delete, matching the expunged_at column the rest of the schema uses: the
-// blob stays referenced until the retention sweep, so a mistaken delete is
-// recoverable and IMAP clients holding the UID still resolve it.
-//
-// The message is located by mailbox as well as UID, so a caller cannot expunge
-// somebody else's mail by guessing a number.
-func (r *WebmailRepository) Expunge(
-	ctx context.Context, mailboxID, folderName string, uid uint32,
-) error {
-	tx, err := r.pool.Begin(ctx)
-	if err != nil {
-		return err
-	}
-	defer tx.Rollback(ctx)
-
-	var messageID uuid.UUID
-	var folderID string
-	var wasUnread bool
-	err = tx.QueryRow(ctx, `
-		SELECT e.id, f.id::text,
-		       NOT EXISTS (SELECT 1 FROM message_flags mf
-		                    WHERE mf.message_id = e.id
-		                      AND mf.received_at = e.received_at
-		                      AND mf.flag = '\Seen')
-		  FROM email_messages e
-		  JOIN folders f ON f.id = e.folder_id
-		 WHERE e.mailbox_id = $1 AND `+folderCondition+`
-		   AND e.uid = $3 AND e.expunged_at IS NULL
-	`, mailboxID, folderName, int64(uid)).Scan(&messageID, &folderID, &wasUnread)
-	if errors.Is(err, pgx.ErrNoRows) {
-		return ErrMessageNotFound
-	}
-	if err != nil {
-		return err
-	}
-
-	if _, err := tx.Exec(ctx,
-		`UPDATE email_messages SET expunged_at = NOW() WHERE id = $1`, messageID); err != nil {
-		return err
-	}
-
-	// GREATEST guards the counters against ever going negative, which a
-	// double expunge of the same row would otherwise cause.
-	unreadDelta := 0
-	if wasUnread {
-		unreadDelta = -1
-	}
-	if _, err := tx.Exec(ctx, `
-		UPDATE folders
-		   SET total_count = GREATEST(0, total_count - 1),
-		       unread_count = GREATEST(0, unread_count + $2),
-		       highest_modseq = highest_modseq + 1
-		 WHERE id = $1
-	`, folderID, unreadDelta); err != nil {
-		return err
-	}
-
-	return tx.Commit(ctx)
-}
-
-// MoveToTrash relocates one message into the mailbox's Trash folder and
-// returns the UID it was given there.
-//
-// This is what "delete" means in a mail client, and the webmail had no way to
-// do it at all: the only removal in the codebase was Expunge, reachable solely
-// when an autosave superseded a draft. A message the user wanted rid of - the
-// empty draft left behind by a sent message, most visibly - could not be
-// removed from any screen.
-//
-// The message keeps its identity and its blob; only the folder and the UID
-// change, because a UID is meaningful only within one folder. Deleting from
-// Trash itself is Expunge's job, not this one's.
-func (r *WebmailRepository) MoveToTrash(
-	ctx context.Context, mailboxID, folderName string, uid uint32,
-) (uint32, error) {
-	return r.moveInto(ctx, mailboxID, folderName, uid, trashTarget)
-}
-
-// MoveToFolder files one message into a named folder.
-//
-// The target is matched on its special-use role or its name, the same way the
-// rest of this repository addresses folders, so "archive" and "Archive" both
-// reach the same place and a folder the user created themselves - which has no
-// role - is reachable by name.
-func (r *WebmailRepository) MoveToFolder(
-	ctx context.Context, mailboxID, folderName string, uid uint32, target string,
-) (uint32, error) {
-	return r.moveInto(ctx, mailboxID, folderName, uid, target)
+	return nil
 }
 
 // trashTarget is what MoveToTrash resolves; kept as a constant so the two
 // callers cannot drift.
 const trashTarget = "trash"
 
-func (r *WebmailRepository) moveInto(
-	ctx context.Context, mailboxID, folderName string, uid uint32, target string,
-) (uint32, error) {
-	tx, err := r.pool.Begin(ctx)
-	if err != nil {
-		return 0, err
-	}
-	defer tx.Rollback(ctx)
-
-	var messageID uuid.UUID
-	var sourceFolderID string
-	var wasUnread bool
-	err = tx.QueryRow(ctx, `
-		SELECT e.id, f.id::text,
-		       NOT EXISTS (SELECT 1 FROM message_flags mf
-		                    WHERE mf.message_id = e.id
-		                      AND mf.received_at = e.received_at
-		                      AND mf.flag = '\Seen')
-		  FROM email_messages e
-		  JOIN folders f ON f.id = e.folder_id
-		 WHERE e.mailbox_id = $1 AND `+folderCondition+`
-		   AND e.uid = $3 AND e.expunged_at IS NULL
-	`, mailboxID, folderName, int64(uid)).Scan(&messageID, &sourceFolderID, &wasUnread)
-	if errors.Is(err, pgx.ErrNoRows) {
-		return 0, ErrMessageNotFound
-	}
-	if err != nil {
-		return 0, err
-	}
-
-	// Deleting something already in Trash has no further destination, so the
-	// caller is told to expunge instead of the message being moved onto itself.
-	var trashFolderID string
-	var trashUID int64
-	err = tx.QueryRow(ctx, `
-		SELECT id::text, uid_next FROM folders
-		 WHERE mailbox_id = $1 AND (special_use = LOWER($2) OR LOWER(name) = LOWER($2))
-		 ORDER BY special_use IS NOT NULL DESC
-		 LIMIT 1
-		 FOR UPDATE
-	`, mailboxID, target).Scan(&trashFolderID, &trashUID)
-	if errors.Is(err, pgx.ErrNoRows) {
-		return 0, port.ErrNoTrashFolder
-	}
-	if err != nil {
-		return 0, err
-	}
-	if trashFolderID == sourceFolderID {
-		return 0, port.ErrAlreadyInTrash
-	}
-
-	var modseq int64
-	if err := tx.QueryRow(ctx, `
-		UPDATE folders SET uid_next = uid_next + 1, highest_modseq = highest_modseq + 1,
-		       total_count = total_count + 1, unread_count = unread_count + $2
-		 WHERE id = $1
-		 RETURNING highest_modseq
-	`, trashFolderID, boolToInt(wasUnread)).Scan(&modseq); err != nil {
-		return 0, err
-	}
-
-	if _, err := tx.Exec(ctx, `
-		UPDATE email_messages SET folder_id = $2, uid = $3, modseq = $4
-		 WHERE id = $1
-	`, messageID, trashFolderID, trashUID, modseq); err != nil {
-		return 0, err
-	}
-
-	unreadDelta := 0
-	if wasUnread {
-		unreadDelta = -1
-	}
-	if _, err := tx.Exec(ctx, `
-		UPDATE folders
-		   SET total_count = GREATEST(0, total_count - 1),
-		       unread_count = GREATEST(0, unread_count + $2),
-		       highest_modseq = highest_modseq + 1
-		 WHERE id = $1
-	`, sourceFolderID, unreadDelta); err != nil {
-		return 0, err
-	}
-
-	if err := tx.Commit(ctx); err != nil {
-		return 0, err
-	}
-	return uint32(trashUID), nil
+// MoveToTrash is what "delete" means in a mail client: the message goes to the
+// Trash folder and keeps its identity. Deleting from Trash itself is Expunge's
+// job, so asking to move out of Trash reports port.ErrAlreadyInTrash.
+func (r *WebmailRepository) MoveToTrash(ctx context.Context, mailboxID, folderName string, uid uint32) (uint32, error) {
+	return r.moveInto(ctx, mailboxID, folderName, uid, trashTarget)
 }
 
-func boolToInt(b bool) int {
-	if b {
-		return 1
+// MoveToFolder files one message into a named folder, matched by role or name.
+func (r *WebmailRepository) MoveToFolder(ctx context.Context, mailboxID, folderName string, uid uint32, target string) (uint32, error) {
+	return r.moveInto(ctx, mailboxID, folderName, uid, target)
+}
+
+func (r *WebmailRepository) moveInto(ctx context.Context, mailboxID, folderName string, uid uint32, target string) (uint32, error) {
+	sourceID, err := r.messageFolder(ctx, mailboxID, folderName)
+	if err != nil {
+		return 0, err
 	}
-	return 0
+	destID, err := r.store.ResolveFolder(ctx, mailboxID, target)
+	if errors.Is(err, port.ErrFolderMissing) {
+		if target == trashTarget {
+			return 0, port.ErrNoTrashFolder
+		}
+		return 0, port.ErrFolderMissing
+	}
+	if err != nil {
+		return 0, err
+	}
+	if destID == sourceID {
+		return 0, port.ErrAlreadyInTrash
+	}
+	return r.store.Move(ctx, sourceID, uid, destID)
 }
 
 // --- folders the mailbox owner creates for themselves --------------------
@@ -507,20 +234,12 @@ func (r *WebmailRepository) RenameFolder(ctx context.Context, mailboxID, from, t
 	return nil
 }
 
-// DeleteFolder removes a folder and the mail filed in it.
-//
-// The messages are expunged rather than deleted outright, matching what the
-// rest of the schema does: the blobs stay referenced until the retention sweep,
-// so a folder deleted by mistake is still recoverable from the database.
+// DeleteFolder removes a folder the owner made, and the mail filed in it. The
+// messages are expunged (recoverable) and their bytes go back to the quota,
+// both inside MailStore.
 func (r *WebmailRepository) DeleteFolder(ctx context.Context, mailboxID, name string) error {
-	tx, err := r.pool.Begin(ctx)
-	if err != nil {
-		return err
-	}
-	defer tx.Rollback(ctx)
-
 	var folderID string
-	err = tx.QueryRow(ctx, `
+	err := r.pool.QueryRow(ctx, `
 		SELECT id::text FROM folders
 		 WHERE mailbox_id = $1 AND LOWER(name) = LOWER($2) AND special_use IS NULL
 	`, mailboxID, name).Scan(&folderID)
@@ -530,16 +249,5 @@ func (r *WebmailRepository) DeleteFolder(ctx context.Context, mailboxID, name st
 	if err != nil {
 		return err
 	}
-
-	if _, err := tx.Exec(ctx, `
-		UPDATE email_messages SET expunged_at = NOW()
-		 WHERE folder_id = $1 AND expunged_at IS NULL
-	`, folderID); err != nil {
-		return fmt.Errorf("expunge the folder's messages: %w", err)
-	}
-
-	if _, err := tx.Exec(ctx, `DELETE FROM folders WHERE id = $1`, folderID); err != nil {
-		return fmt.Errorf("delete folder %q: %w", name, err)
-	}
-	return tx.Commit(ctx)
+	return r.store.DeleteFolder(ctx, folderID)
 }