From: Mustafa Akgul (akgul@Bilkent.EDU.TR)
Date: Tue 10 Jul 2001 - 17:08:40 EEST
Subject: A small victory: Postfix/ezmlm
To: Postfix users <postfix-users@postfix.org>
Date: Tue, 10 Jul 2001 09:34:17 -0400 (EDT)
X-Time-Zone: USA EST, 6 hours behind central European time
X-Mailer: ELM [version 2.4ME+ PL82 (25)]
From: wietse@porcupine.org (Wietse Venema)
According to yesterday's Postfix release announcement:
>- QMQP server support, so that Postfix can be used as backend mailer
>for the ezmlm-idx mailing list manager. You still need one qmail
>system to drive ezmlm. But you can feed any number of Postfix mail
>delivery engines in this manner.
What is this cryptic note about?
Securityfocus (bugtraq etc.) was having performance problems in
May this year. They were using Listserv as the list manager, and
Postfix for mail delivery. However, Listserv could no longer keep
up with the traffic, and the backlog kept growing and growing.
Securityfocus switched from listserv+postfix to (ezmlm+qmail)+postfix.
Changing to the ezmlm mailing list manager meant they had to use
qmail, because ezmlm works with nothing else. Securityfocus used
the same Solaris machine for (ezmlm+qmail) as had been used for
(listserv+postfix). Shortly before the change of list manager they
added two Linux machines running Postfix for the final delivery.
After this list manager change, performance improved, but mail was
still experiencing several hours of delay as qmail was feeding the
mail into the Postfix machines - over an internal network!! The
Postfix machines added only a few minutes of delay, and that was
with mail delivery over the entire Internet.
This weekend I added a qmail protocol to Postfix so that the ezmlm
list manager can feed its mail directly into any number of Postfix
machines. Yesterday the code was released after a lot of testing.
Securityfocus put it into operation a few hours later. As a result,
their mail delays have gone down by a factor of 10. Victory!!
By the way, that qmail protocol should have been unnecessary.
Postfix implements SMTP with command pipelining as per RFC standards.
That protocol should have been used instead.
As the announcement says:
>- QMQP server support, so that Postfix can be used as backend mailer
>for the ezmlm-idx mailing list manager. You still need one qmail
>system to drive ezmlm. But you can feed any number of Postfix mail
>delivery engines in this manner.
I was concerned that Bernstein would get all the Securityfocus mail
delivery for the wrong reason, namely, that Bernstein's list manager
software does not work with other people's mail delivery software.
Strike one: by making ezmlm feed mailings directly into Postfix I
have eliminated Securityfocus's mail delivery performance problem.
Strike two will be to eliminate the requirement that qmail drives
the ezmlm list manager, thereby eliminating the need for qmail.
That is the easier part. I just had to solve the more difficult
delivery performance problem first.
Wietse
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