Fix: Set Message-Id and Date headers on outgoing emails (#115)

* fix: set Message-Id and Date headers on outgoing emails

Emails sent via the MCP server are missing Message-Id and Date headers.
When using iCloud SMTP (and similar providers), these headers are assigned
server-side during delivery, but they don't appear in the copy saved to
the IMAP Sent folder via APPEND. This breaks email threading in clients
like Apple Mail, which build the References chain from the Sent folder
copy rather than the delivered message.

Generate Message-Id (via email.utils.make_msgid) and Date (via
email.utils.formatdate) headers on the message object before both
sending via SMTP and saving to the Sent folder, so the same values
appear in both copies.

* test: add tests for Message-Id and Date header generation

Cover header presence and domain extraction from the sender address,
and verify the same Message-Id and Date appear on both the SMTP-sent
message and the returned object used for IMAP Sent folder saving.

Author: frlefebvre

mcp_email_server/emails/classic.py

@@ -776,6 +776,12 @@ async def send_email(
         if references:
             msg["References"] = references
 
+        # Set Date and Message-Id headers so the same values appear in both
+        # the SMTP-sent copy and the IMAP Sent folder copy
+        msg["Date"] = email.utils.formatdate(localtime=True)
+        sender_domain = self.sender.rsplit("@", 1)[-1].rstrip(">")
+        msg["Message-Id"] = email.utils.make_msgid(domain=sender_domain)
+
         # Note: BCC recipients are not added to headers (they remain hidden)
         # but will be included in the actual recipients for SMTP delivery
 

tests/test_email_client.py

@@ -328,6 +328,67 @@ async def test_send_email(self, email_client):
             assert "bcc@example.com" in recipients
 
 
+class TestSendEmailMessageIdAndDate:
+    @pytest.mark.asyncio
+    async def test_send_email_sets_message_id_and_date(self, email_client):
+        """Test that send_email sets Message-Id and Date headers."""
+        mock_smtp = AsyncMock()
+        mock_smtp.__aenter__.return_value = mock_smtp
+        mock_smtp.__aexit__.return_value = None
+        mock_smtp.login = AsyncMock()
+        mock_smtp.send_message = AsyncMock()
+
+        with patch("aiosmtplib.SMTP", return_value=mock_smtp):
+            msg = await email_client.send_email(
+                recipients=["recipient@example.com"],
+                subject="Test Subject",
+                body="Test Body",
+            )
+
+            assert msg["Message-Id"] is not None
+            assert "@example.com>" in msg["Message-Id"]
+            assert msg["Date"] is not None
+
+    @pytest.mark.asyncio
+    async def test_send_email_message_id_uses_sender_domain(self, email_server):
+        """Test that Message-Id domain is extracted from the sender address."""
+        client = EmailClient(email_server, sender="user@getsequel.app")
+        mock_smtp = AsyncMock()
+        mock_smtp.__aenter__.return_value = mock_smtp
+        mock_smtp.__aexit__.return_value = None
+        mock_smtp.login = AsyncMock()
+        mock_smtp.send_message = AsyncMock()
+
+        with patch("aiosmtplib.SMTP", return_value=mock_smtp):
+            msg = await client.send_email(
+                recipients=["recipient@example.com"],
+                subject="Test",
+                body="Body",
+            )
+
+            assert "@getsequel.app>" in msg["Message-Id"]
+
+    @pytest.mark.asyncio
+    async def test_send_email_same_message_on_smtp_and_return(self, email_client):
+        """Test that the same msg object (with Message-Id) is sent and returned."""
+        mock_smtp = AsyncMock()
+        mock_smtp.__aenter__.return_value = mock_smtp
+        mock_smtp.__aexit__.return_value = None
+        mock_smtp.login = AsyncMock()
+        mock_smtp.send_message = AsyncMock()
+
+        with patch("aiosmtplib.SMTP", return_value=mock_smtp):
+            returned_msg = await email_client.send_email(
+                recipients=["recipient@example.com"],
+                subject="Test",
+                body="Body",
+            )
+
+            sent_msg = mock_smtp.send_message.call_args[0][0]
+            assert sent_msg["Message-Id"] == returned_msg["Message-Id"]
+            assert sent_msg["Date"] == returned_msg["Date"]
+
+
 class TestParseEmailData:
     def test_parse_email_extracts_message_id(self, email_client):
         """Test that Message-ID header is extracted during parsing."""