Hello,

i've been googling about this term but i'm not so sure.
what is the best mail server for a high load server ?

High load server means a server with 150 domains (at least) and 2000 email accounts.
I usually use qmail or qmail+ldap, and the performance is ok, but i've been thinking about changing to another MTA. Is it worth ?
And if it's worth, what is a good option ?

I've read that the common choice is postfix, but i don't know if it's only for low load (i.e. for home servers) or if it's a good option too for high load.

Has anybody some experiences ? can anybody share them with me ?
What Mail server do you recommend? Postfix? Exim? or do i go on with qmail ?

Regards and thank you in advance.

I think qmail is the fastest MTA.

But postfix is a good option. Actually if you have a huge email traffic reducing the I/O wait will be the best solution (with raid systems like 8 disk raid 10). I think most of the MTA have the same performance.

Good day.

AT my last Job we setup a mail server running postfix using it in a virtual mail setup to host serveral (that being When I remember setup of the server 30 / each with about 5 to 30 people) domains. This thing ran great course it was using 2 or 4 quad core processors and about 12 gig of ram. But single server had no troubles at all.

I used to work at an ISP
They used exim

I can remember that in my old job, we used exim because of we use Cpanel and exim comes with CPanel. Besides, it works great with a lot of domains and accounts (300 domains aproximately)
But i think and i've read that has a much more harder configuration than the others.

Moreover, i've never used sendmail/postfix (or others) in production with lots of domains and i don't know how they'd behave.
So i prefer to listen your recommendations and after decide.

Thank you very much.

No more suggestions ?

That's pretty much all the suggestions there are to be made. The most popular Open Source MTAs are Exim, Postfix, Sendmail, and Qmail.

In my experience none of them are clearly faster than the rest. Postfix is probably the easiest to configure, Sendmail is probably the hardest. Your ability to effectively configure the MTA and the way you configure the OS and hardware are probably going to have a lot more effect on the performance than which MTA you choose. Given that it's probably best to stick to Qmail and concentrate on learning advanced performance tuning tricks.

You can get huge increases in performance by putting temporary queues on RAMdisks (make sure you understand the risks, though!), spreading the spool over more physical spindles, etc.

Thanks to everybody for answering, i'm going to continue using qmail but i'm going to try postfix once too.

Regards.

The definition of "high-load" you're using could mean anything. Number of domains and accounts isn't really the relevant measure of a servers load, the volume of email it typically transmits is.

I've done ~1k domains, ~30k vaccounts on sendmail in the past, with a mail volume of a million or so messages a day (This was many years ago (late 90s), the volume on the same domains would be considerably higher today... and keep in mind thats what the final destination box saw, not what the outside filtering machines had hitting them.)

Honestly, if you're satisfied with qmail and the scalability of it, stick with qmail, why fix what isn't broken unless there is a compelling feature related reason.

I have ~30 domains/~150 boxes hosted on my personal server presently, 29 of them get ~<1000 email a day including spam. 1 gets 25-125k email a day... almost all spam. The load rarely goes above .25 and it's running a lot of inefficient processes since its a solitary machine doing web, mail (with spamfiltering, avfilterings, uribls, greylisting, black/whitelisting, etc), dns, and several other services. The machine isn't an impressive piece of hardware by any stretch of the imagination either.

Postfix, QMail, Sendmail, and Exim will all scale to pretty much whatever you need them to do with the right configuration in all but the highest volume mail situations.