1 This patch comes from upstream:

     2 

     3 https://hg.python.org/cpython/rev/d590114c2394

     4 

     5 --- a/Lib/smtplib.py	Sun Nov 08 01:03:52 2015 -0500

     6 +++ b/Lib/smtplib.py	Sat Jun 11 13:18:56 2016 -0700

     7 @@ -656,6 +656,11 @@

     8              self.ehlo_resp = None

     9              self.esmtp_features = {}

    10              self.does_esmtp = 0

    11 +        else:

    12 +            # RFC 3207:

    13 +            # 501 Syntax error (no parameters allowed)

    14 +            # 454 TLS not available due to temporary reason

    15 +            raise SMTPResponseException(resp, reply)

    16          return (resp, reply)

    17  

    18      def sendmail(self, from_addr, to_addrs, msg, mail_options=[],