按SMTP信封限定投递收件人并对齐通知配额

backend/dto/parsemail/email.go

@@ -76,6 +76,7 @@ type Email struct {
 	InReplyTo        string
 	ThreadReferences string
 	EnvelopeFrom     string
+	EnvelopeTo       []*User `json:"-"`
 	ReplyTo          []*User
 	From             *User
 	To               []*User

backend/listen/smtp_server/notification.go

@@ -50,7 +50,7 @@ func (s *Session) prepareNotification(email *parsemail.Email, rawBytes int) erro
 			return &smtp.SMTPError{Code: 550, EnhancedCode: smtp.EnhancedCode{5, 7, 1}, Message: "Notification recipient is not authorized by envelope"}
 		}
 	}
-	if err := s.authorization.ReserveNotification(len(recipients)); err != nil {
+	if err := s.authorization.ReserveNotification(len(s.To)); err != nil {
 		if errors.Is(err, notification.ErrQuota) {
 			return &smtp.SMTPError{Code: 452, EnhancedCode: smtp.EnhancedCode{4, 7, 0}, Message: "Notification sending quota exceeded"}
 		}

backend/listen/smtp_server/read_content.go

@@ -180,6 +180,10 @@ func (s *Session) Data(r io.Reader) (resultErr error) {
 				return send.SendTriggered(ctx, email, "系统通知 SMTP 发信")
 			}
 		}
+		email.EnvelopeTo = make([]*parsemail.User, len(s.To))
+		for index, address := range s.To {
+			email.EnvelopeTo[index] = &parsemail.User{EmailAddress: address}
+		}
 		resultErr = s.deliverOutgoingEmail(email, sender)
 		if resultErr == nil {
 			result = "accepted"

backend/utils/send/send.go

@@ -120,16 +120,23 @@ func sendRecipients(ctx *context.Context, e *parsemail.Email, recipients []*pars
 		return fmt.Errorf("build message: %w", err), nil
 	}
 
-	var to []*parsemail.User
-	to = append(append(append(to, e.To...), e.Cc...), e.Bcc...)
-	if recipients != nil {
-		to = recipients
-	}
+	to := deliveryRecipients(e, recipients)
 
 	return doSend(ctx, fromDomain, b, to, e.From.EmailAddress, trigger)
 
 }
 
+func deliveryRecipients(e *parsemail.Email, recipients []*parsemail.User) []*parsemail.User {
+	if recipients != nil {
+		return recipients
+	}
+	if e.EnvelopeTo != nil {
+		return e.EnvelopeTo
+	}
+	var targets []*parsemail.User
+	return append(append(append(targets, e.To...), e.Cc...), e.Bcc...)
+}
+
 func parseRecipientAddress(user *parsemail.User) (string, string, error) {
 	if user == nil {
 		return "", "", errors.New("recipient is nil")

backend/utils/send/send_test.go

@@ -158,3 +158,43 @@ func TestDoSendRejectsEmptyRecipientList(t *testing.T) {
 		t.Fatalf("failure count = %d, want 1", len(failures))
 	}
 }
+
+func TestDeliveryRecipientsKeepsEnvelopeSeparateFromHeaders(t *testing.T) {
+	to := &parsemail.User{EmailAddress: "header-to@example.com"}
+	cc := &parsemail.User{EmailAddress: "header-cc@example.com"}
+	bcc := &parsemail.User{EmailAddress: "header-bcc@example.com"}
+	envelope := &parsemail.User{EmailAddress: "envelope@example.com"}
+	queued := &parsemail.User{EmailAddress: "queued@example.com"}
+	tests := []struct {
+		name     string
+		envelope []*parsemail.User
+		override []*parsemail.User
+		want     []*parsemail.User
+	}{
+		{name: "web message uses header recipients", want: []*parsemail.User{to, cc, bcc}},
+		{name: "smtp uses accepted envelope only", envelope: []*parsemail.User{envelope}, want: []*parsemail.User{envelope}},
+		{name: "empty envelope never falls back to headers", envelope: []*parsemail.User{}},
+		{name: "queue uses its single recipient", envelope: []*parsemail.User{envelope}, override: []*parsemail.User{queued}, want: []*parsemail.User{queued}},
+		{name: "explicit empty override never falls back", envelope: []*parsemail.User{envelope}, override: []*parsemail.User{}},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			message := &parsemail.Email{
+				To: []*parsemail.User{to}, Cc: []*parsemail.User{cc}, Bcc: []*parsemail.User{bcc},
+				EnvelopeTo: tt.envelope,
+			}
+			got := deliveryRecipients(message, tt.override)
+			if len(got) != len(tt.want) {
+				t.Fatalf("recipient count = %d, want %d", len(got), len(tt.want))
+			}
+			for index := range got {
+				if got[index] != tt.want[index] {
+					t.Fatalf("recipient %d = %v, want %v", index, got[index], tt.want[index])
+				}
+			}
+			if len(message.To) != 1 || message.To[0] != to || len(message.Cc) != 1 || message.Cc[0] != cc || len(message.Bcc) != 1 || message.Bcc[0] != bcc {
+				t.Fatal("delivery routing changed the message headers")
+			}
+		})
+	}
+}