feat: enforce Mail-owned campaign transport boundary

tests/test_imap_parser.py

@@ -247,6 +247,22 @@ class ImapMailboxCommandTests(unittest.TestCase):
         self.assertEqual(result.folder, "Gesendete Elemente")
         self.assertEqual(result.bytes_appended, len(b"Subject: test\r\n\r\nBody"))
 
+    def test_connection_loss_after_append_starts_has_unknown_outcome(self):
+        class Client:
+            def append(self, _mailbox, _flags, _date_time, _message):
+                raise OSError("provider detail")
+
+            def logout(self):
+                return "BYE", [b"logged out"]
+
+        config = ImapConfig(host="imap.example.org", username="user", password="secret", sent_folder="Sent")
+        with patch("govoplan_mail.backend.sending.imap._open_imap", return_value=Client()):
+            with self.assertRaises(ImapAppendError) as captured:
+                append_message_to_sent(b"Subject: test\r\n\r\nBody", imap_config=config, folder="Sent")
+
+        self.assertTrue(captured.exception.outcome_unknown)
+        self.assertFalse(captured.exception.temporary)
+
 
 if __name__ == "__main__":
     unittest.main()