[Mailman-Users] Mailman is failing to send mails to a list cantaining more than 80 mail-ids

Mark Sapiro mark at msapiro.net
Thu Jan 13 17:58:32 CET 2011

Manthra wrote:
>We have Mailman with Postfix (Virtual)  running successfuly with small
>mailing lists(i.e. Having less than just 80 mail-ids in the lists).  But if
>the size of the mailinglist goes beyond 80 mail-ids, it is failing to send
>We have  tried setting up  the option "Ceiling on acceptable number of
>recipients for a posting"
>to 400,  but  no use.

This setting has no effect whatsoever on this issue. This setting will
cause an incoming post to be held if the number of explicit To: and
Cc: recipient addresses equals or exceeds that number. It has nothing
to do with how a post is delivered.

>We are getting the following error in the log file
>/var/lib/mailman/logs/smtp-failure         (only when list size crosses 80
>Jan 13 11:47:18 2011 (27459) delivery to manthra.24 at gmail.com failed with
>code -1: Server not connected
>Same error for all the email-ids in the list

Something is causing Postfix to disconnect when the recipient list for
the mail exceeds 80 addresses. My best guess is that 25% of your list
addresses are invalid and Postfix is doing recipient address
verification and disconnecting with a 421 error after 20 invalid
addresses. There is a bug in the Python SMTP library
<http://bugs.python.org/issue5713> that can cause the above error when
this occurs.

Regardless of whether or not the above conjecture is correct, try


in mm_cfg.py and restarting Mailman. This will cause Mailman to deliver
list mail to Postfix in separate transactions with no more than 20
recipients each and should solve the problem.

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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