When using smtplib.SMTP to connect to a SMTP server the instance variables esmtp_response survives a SMTP.quit() which results in the following error:

>>> import smtplib
>>> smtp = smtplib.SMTP('mail.oberkirch.org', 25)
>>> smtp.starttls()
(220, b'2.0.0 Ready to start TLS')
>>> smtp.ehlo()
(250, b'mail.oberkirch.org\nPIPELINING\nSIZE 10240000\nVRFY\nETRN\nAUTH PLAIN LOGIN\nAUTH=PLAIN LOGIN\nENHANCEDSTATUSCODES\n8BITMIME\nDSN')
>>> smtp.quit()
(221, b'2.0.0 Bye')
>>> smtp.connect('mail.oberkirch.org', 25)
(220, b'mail.oberkirch.org ESMTP Postfix')
>>> smtp.starttls()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.4/smtplib.py", line 672, in starttls
    raise SMTPException("STARTTLS extension not supported by server.")
smtplib.SMTPException: STARTTLS extension not supported by server.
>>>

While reporting this issue I found out that starttls also does not throw away any ehlo information as it should. Provided that fixing this would probably break existing code (which would only work with non-standard servers like postfix) I did not change that behaviour.

Thanks, Milan.

I could swear I typed a '6' in the commit message, but apparently not...

New changeset a058760cb069 by R David Murray in branch '3.4':
#22215: have the smtplib 'quit' command reset the state.
http://hg.python.org/cpython/rev/a058760cb069

New changeset d0d4ab0ba70e by R David Murray in branch 'default':
Merge #22215: have the smtplib 'quit' command reset the state.
http://hg.python.org/cpython/rev/d0d4ab0ba70e

New changeset 7288519594de by R David Murray in branch '2.7':
#22215: have the smtplib 'quit' command reset the state.
http://hg.python.org/cpython/rev/7288519594de