handoff fixes

backend/tests/test_mail_sender.py

@@ -41,3 +41,50 @@ async def test_send_via_smtp_uses_configured_client_hostname():
         )
 
     assert send_mock.await_args.kwargs["local_hostname"] == "backend.gentic.email"
+
+
+def test_build_message_sets_in_reply_to_and_references():
+    message = build_message(
+        sender="suyash@gentic.email",
+        recipients=["customer@gmail.com"],
+        cc=[],
+        subject="Re: fresh test",
+        body_text="human said B",
+        body_html=None,
+        in_reply_to="<CAHabc123@mail.gmail.com>",
+        references=["<CAHabc123@mail.gmail.com>"],
+        message_id="<B@gentic.email>",
+    )
+    assert message["Message-ID"] == "<B@gentic.email>"
+    assert message["In-Reply-To"] == "<CAHabc123@mail.gmail.com>"
+    assert message["References"] == "<CAHabc123@mail.gmail.com>"
+    raw = message.as_bytes()
+    assert b"In-Reply-To: <CAHabc123@mail.gmail.com>" in raw
+    assert b"References: <CAHabc123@mail.gmail.com>" in raw
+
+
+def test_signed_mime_preserves_in_reply_to():
+    from unittest.mock import patch
+
+    message = build_message(
+        sender="suyash@gentic.email",
+        recipients=["customer@gmail.com"],
+        cc=[],
+        subject="Re: fresh test",
+        body_text="human said B",
+        body_html=None,
+        in_reply_to="<CAHabc123@mail.gmail.com>",
+        references=["<CAHabc123@mail.gmail.com>"],
+        message_id="<B@gentic.email>",
+    )
+    domain = SimpleNamespace(
+        domain_name="gentic.email",
+        dkim_selector="agmail",
+        dkim_private_key="private-key",
+    )
+    with patch(
+        "app.services.mail_sender.dkim.sign",
+        return_value=b"DKIM-Signature: test\r\n",
+    ):
+        signed = sign_message(message, domain)
+    assert b"In-Reply-To: <CAHabc123@mail.gmail.com>" in signed