Fix IMAP Sent copy hanging after SMTP delivery

internal/mailbox/imap.go

@@ -229,7 +229,10 @@ func (t *imapTransport) Send(_ context.Context, from string, d Draft) (SendResul
 	}
 	// Best-effort copy to Sent so the message shows in the member's mailbox.
 	t.mu.Lock()
-	_, _ = t.c.Append(Sent, int64(len(msg)), nil).Wait() // ignore APPEND errors
+	appendCmd := t.c.Append(Sent, int64(len(msg)), nil)
+	_, _ = appendCmd.Write(msg)
+	_ = appendCmd.Close()
+	_, _ = appendCmd.Wait()
 	t.mu.Unlock()
 	return SendResult{MessageID: msgID}, nil
 }

internal/mailbox/imap_test.go

@@ -0,0 +1,91 @@
+package mailbox
+
+import (
+	"context"
+	"net"
+	"testing"
+
+	"github.com/emersion/go-imap/v2"
+	"github.com/emersion/go-imap/v2/imapserver"
+	"github.com/emersion/go-imap/v2/imapserver/imapmemserver"
+)
+
+func newFakeIMAP(t *testing.T) string {
+	t.Helper()
+
+	backend := imapmemserver.New()
+	user := imapmemserver.NewUser("alice", "secret")
+	if err := user.Create(Inbox, nil); err != nil {
+		t.Fatal(err)
+	}
+	if err := user.Create(Sent, nil); err != nil {
+		t.Fatal(err)
+	}
+	backend.AddUser(user)
+
+	server := imapserver.New(&imapserver.Options{
+		NewSession: func(*imapserver.Conn) (imapserver.Session, *imapserver.GreetingData, error) {
+			return backend.NewSession(), nil, nil
+		},
+		InsecureAuth: true,
+		Caps: imap.CapSet{
+			imap.CapIMAP4rev1: {},
+			imap.CapIMAP4rev2: {},
+		},
+	})
+	listener, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	go func() { _ = server.Serve(listener) }()
+	t.Cleanup(func() {
+		_ = server.Close()
+		_ = listener.Close()
+	})
+	return listener.Addr().String()
+}
+
+func TestIMAPSendCopiesMessageToSent(t *testing.T) {
+	smtpServer := newFakeSMTP(t)
+	transport, err := NewIMAPTransport(IMAPConfig{
+		IMAPAddr:  newFakeIMAP(t),
+		SMTPAddr:  smtpServer.addr,
+		Username:  "alice",
+		Password:  "secret",
+		Plaintext: true,
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { _ = transport.Close() })
+
+	_, err = transport.Send(context.Background(), "alice@example.test", Draft{
+		To:      []Address{{Address: "bob@example.test"}},
+		Subject: "Saved message",
+		Text:    "message body",
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	messages, err := transport.ListMessages(context.Background(), ListOptions{Mailbox: Sent})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(messages) != 1 {
+		t.Fatalf("Sent contains %d messages; want 1", len(messages))
+	}
+	if messages[0].Subject != "Saved message" {
+		t.Fatalf("Sent subject = %q; want %q", messages[0].Subject, "Saved message")
+	}
+	message, found, err := transport.ReadMessage(context.Background(), Sent, messages[0].UID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !found {
+		t.Fatal("saved message not found in Sent")
+	}
+	if message.Text != "message body" {
+		t.Fatalf("Sent body = %q; want %q", message.Text, "message body")
+	}
+}