--- a/mercurial/mail.py	Mon Jul 16 18:16:26 2018 -0400
+++ b/mercurial/mail.py	Mon Jul 16 18:17:19 2018 -0400
@@ -79,7 +79,7 @@
                                         self.keyfile, self.certfile,
                                         ui=self._ui,
                                         serverhostname=self._host)
-        self.file = smtplib.SSLFakeFile(new_socket)
+        self.file = new_socket.makefile(r'rb')
         return new_socket
 
 def _pyhastls():