[Mailman-Users] mailman + postfix = strange behaviour

Mark Sapiro mark at msapiro.net
Thu Aug 20 20:02:09 CEST 2009

Marek Kozlowski wrote:

>error: no error messages
>post: only "post to ... <nr_of_group_members> failures"
>qrunner: no error messages
>smtp: no error messages
>smtp-failure: that's it! Lots of errors like:

>"Aug 20 18:50:10 2009 (15479) delivery to someuser at mini.pw.edu.pl failed 
>with code -1: Server not connected"

See below:

And Marek Kozlowski wrote:

>I've found some suggestion to set SMTPPORT to 25 (it is... 0 ?) in 
>mm_cfg.py. Now I have:

>"Aug 20 19:11:13 2009 (21289) delivery to someuser at mini.pw.edu.pl failed 
>with code -1: (104, 'Connection reset by peer')"

The fact that the error changed when you set SMTPPORT = 25 rather than
the Defaults.py setting of 0 is a coincidence. There is no difference
between the two. SMTPPORT = 25 tells the python smtplib module to use
port 25 and SMTPPORT = 0 tells it to use the SMTP default port which
is 25.

And Marek Kozlowski wrote:

>-- thanks Mark!)
>helped. Still I'mnot sure why :-(

It helps because of a bug in the underlying Python smtplib. See

Your real problem is you have addresses on your list that Postfix
thinks are undeliverable. The bug report linked above describes the

After 20 invalid local recipients in one SMTP transaction, Postfix
disconnects with a 421 Too many errors reply, but the Python smtplib
module doesn't expect a disconnect after a 421 and gets out of sync
with Postfix.

Setting SMTP_MAX_RCPTS to any number less than 20 will avoid this

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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