[Mailman-Users] Delivery to SMTP server very slow

Barry Warsaw barry at python.org
Sun Feb 21 15:38:47 CET 2010

On Feb 20, 2010, at 11:01 PM, Stefan Foerster wrote:

>As expected, Postfix is not the culprit. Delivery to smtp-sink is
>running at the speed of molasses, too.

Now this is getting interesting <wink>.


has some perplexing numbers.  If you're really seeing a 2 second delay between
the reading of one RCPT reply to the next, then this points to problems in
Python or its smtplib module.  I did a quick search through the Python bug
tracker and nothing jumped out at me.

As Mark said, Mailman basically just calls SMTP.sendmail() to send the message
to each chunk of recipients.  The part of that method that sends the RCPTs to
Postfix is this code (in Py2.6):

        for each in to_addrs:
            (code,resp)=self.rcpt(each, rcpt_options)
            if (code != 250) and (code != 251):

It's hard to see what would cause that loop to sit there between the 19:03:15
retcode and 19:03:17 send.  You're not even touching the socket between these
calls.  Looking at putcmd() and getreply() and the way they're called, I just
don't see any opportunity for hanging.  I suppose it's possible you're setting
Python issues, but that doesn't really explain why it would affect only this

I probably missed it but what platform are you running on?  What version of

I see that you've worked around the problem, which of course only adds oddness.
If you're still able and interested in debugging this, I can think of a couple
of things to do.  Let me know and I'll lay out a few ideas.


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