[Mailman-Users] Delivery to SMTP server very slow

Mark Sapiro mark at msapiro.net
Sat Feb 20 18:02:19 CET 2010

On 2/20/2010 4:21 AM, Stefan Foerster wrote:
> For all other lists on this server, the conversation between Postfix
> and Mailman is very fast paced, but for that one list, it takes almost
> one second for a recipient to be specified (which is then acknowledged
> immediately by Postfix).

So, without VERP or personalization, you should be seeing SMTP
transactions that look like

(repeated for up to SMTP_MAX_RCPTS recipients)
(message data)
(MAIL FROM through DATA repeats until all recipients are delivered)

And, if I understand what you're saying, the delay is in the RCPT
TO/response loop and it occurs between the response and the next RCPT TO.

This is really wierd. There is not even any Mailman code involved in
this. The entire sequence from MAIL FROM to end of DATA is done by one
call to the Python smtplib.SMTP.sendmail() method.

There is nothing list specific other than the envelope sender in the
sendmail() call/MAIL FROM command in Mailman's interaction with smtplib,
and if it were related somehow to that, I would expect the delay to be
in Postfix between the RCPT TO and response.

> I really don't have any idea where I coul start debugging, or how.

Nor do I really. You could look at the FAQ at
<http://wiki.list.org/x/-IA9> for the way to enable smtplib debugging
(as noted in the FAQ, only for Python 2.4.x and newer). This will
produce voluminous Mailman error log output which may help pinpoint
where in smtplib.py the delay is, but probably the time-stamp
granularity is not fine enough.

Mark Sapiro <mark at msapiro.net>        The highway is for gamblers,
San Francisco Bay Area, California    better use your sense - B. Dylan

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