Re: Qmail/Postfix/Sendmail for fastest outgoing mail
On Mon, Nov 25, 2002 at 03:01:29PM +1100, Jason Lim wrote:
> > however, it won't solve the multiple-recipients-at-one-domain
> > problem. if qmail relays individual messages via a postfix box,
> > then the postfix box will have individual messages in it's queue -
> > it can't recombine them into one message. i.e. the "damage" has
> > already been done.
>
> I don't quite understand that part about the "damage" already being
> done. For example, if Qmail hands Postfix, say, 10 emails
> (individually, as Qmail does), and 5 of those emails is to the same
> domain/mailserver, wouldn't Postfix "combine" them and send them at
> one time?
nope, because postfix has no way of knowing that they were originally
the same email(*). postfix has been handed 10 individual emails by
qmail, so it will deliver 10 individual emails.
postfix is good, but it's not magic.
(*) theoretically, it is possible to scan the headers and/or body to
determine this, but postfix doesn't do it and i doubt if anyone would
implement it. it's just not worth the dev. time (or the increased size
& complexity of code) to do it just to handle this unusual corner-case.
> Of course, if there is significant delay between the messages, such as
> 1 hour, then obviously Postfix won't wait an hour to collect enough
> emails to a particular domain, but say they were sent in succession
> (say 2 seconds apart), since these are mailing list servers and email
> from the Qmail servers tends to go out in a batch rather than
> individually. Wouldn't Postfix combine them in this situation?
nope. you might think of them as just one email, but by the time
postfix gets them they are multiple different emails.
> I was also hoping in some optimization of the actual mail sending as
> well... such as what Sendmail or Postfix could offer in this case. If
> what you say above is what will happen (emails send individually and
> not combined) then in effect setting up the email server as
> qmail/sendmail/postfix won't make any difference, since they would be
> sent individually anyway?
there would be a difference, just not the huge difference you were
hoping for.
postfix would be slightly faster than qmail but not that much faster
that it's worth using different software for - unless part of your
purpose is to get some real (as opposed to testing) experience with
postfix to decide whether it's worth switching.
sendmail isn't a good choice if high-performance is important to you.
overall performance would probably be worse than just keeping things as
they are. (there, that was a very politic way of saying that, wasn't it :)
if you want to fix this problem, you have to do it at the source - i.e.
replace qmail with postfix on your main boxes. that would be a lot of
work, not something to be done lightly.
if you're not using ezmlm, you may be able to hack your list manager to
bypass local qmail and send outgoing messages via SMTP direct to the
postfix box. this may involve hacking the list manager to talk SMTP
rather thank fork /usr/sbin/sendmail, or it may involve replacing
/usr/sbin/sendmail with a wrapper script that talks SMTP. either way,
it's not too hard.
actually, now that i think about it, i remember reading something about
getting ezmlm to work with postfix...i didn't pay much attention because
it required a qmail box as well as postfix, so it might be just right
for your situation. search the postfix-users archive for ezmlm.
craig
--
craig sanders <cas@taz.net.au>
Fabricati Diem, PVNC.
-- motto of the Ankh-Morpork City Watch
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