[Mailman-Users] slow "out" queue

Mark Sapiro mark at msapiro.net
Thu Feb 2 07:56:30 CET 2012

Anil Jangity wrote:

>Does mailman actually (if it works) send to 15 recipients at a time - per SMTP session?

Mailman's use of the term session is not consistent with the RFCs. What
Mailman calls SMTP_MAX_SESSIONS_PER_CONNECTION is actually in RFC 821,
2821, 5321 terms, max transactions per session. I.e. one session is
one connection from HELO/EHLO to QUIT and one transaction is one MAIL
FROM and everything that follows up to the next MAIL FROM.

Unless you have some specific MTA reason for setting
SMTP_MAX_SESSIONS_PER_CONNECTION, you should leave it at the default
value of 0 meaning unlimited.

If a message is personalized or VERPd, SMTP_MAX_RCPTS is ignored
because you can't send a personalized or VERPd message to more than
one recipient. Otherwize, SMTP_MAX_RCPTS is the maximum number of RCPT
TO recipients in one MAIL FROM transaction.

Note that 6000 users per 35 minutes is less than 3 per second. This is
extremely slow. I typically see 30 to over 60 recipients per second on
a rather ordinary production server with full VERP.

See my reply to your original post in this thread at
and look at the FAQs linked in that post for hints. In particular, do
not do DNS verification of RCPT TO domains during SMTP from Mailman.

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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