#13: implement Outbound Queue, Retry Backoff Engine & DSN Bounce Generator (RFC 3464)

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

@@ -0,0 +1,9 @@
+package port
+
+import (
+	"context"
+)
+
+type MXResolver interface {
+	LookupMX(ctx context.Context, domain string) ([]string, error)
+}

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

@@ -0,0 +1,13 @@
+package port
+
+import (
+	"context"
+
+	"lambdamail/protocols/internal/domain/entity"
+)
+
+type OutboundRepository interface {
+	Enqueue(ctx context.Context, job *entity.OutboundJob) error
+	FetchNextReady(ctx context.Context, workerID string, limit int) ([]*entity.OutboundJob, error)
+	UpdateJob(ctx context.Context, job *entity.OutboundJob) error
+}