Comparison between qmail and postfix

Posted on 2008-10-09
Medium Priority
Last Modified: 2013-12-09
Dear all:
  could you teach me , how to comparison the open source between qmail and postfix functional specification.i m no idea on the mail server.
In the Message Tansfer Agent, qmail and postfix also have higt security and performance .
i m search the information about it.
thx your advise.
Question by:janewit
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Assisted Solution

Petr_Sponer earned 320 total points
ID: 22685493
In my opinion qmail is slowly out of question if you seek SW for new server. Qmail is harder to setup and also is significantly harder to maintain. I have experiance with both in larger production environment.
LVL 62

Assisted Solution

gheist earned 760 total points
ID: 22695308
add exim to picture, it integrates viruss scanner, no need for amavis and similar.
qmail is very hard to maintain.

What performance you need? Basically in days when pentium pro 180 was top of the line a machine with blazing 32MB of ram did about 50 messages/ second with so slow and bad sendmail.
Modern machine does same but scans for viruses all mails in transit using exim+clamav

CVE tracks serious security issues in mailers:
qmail - 9
postfix - 15
exim - 11
sendmail - 78

Given you actually have no specification already I'd suggest you look for platform (Linux distribution, OpenSolaris, FreeBSD) where keeping mailer patched will not be nail in down back like with OpenBSD.
LVL 21

Accepted Solution

Daniel McAllister earned 920 total points
ID: 22752905
I couldn't DISAGREE more with the idea that QMail is harder to maintain.

I will say that email servers in GENERAL are harder to maintain for most new admins, because the email structure of the Internet was never really designed for the kinds of uses it has evolved into. However, in my opinion, QMail goes where no other mail server has gone before -- it actually separates out the separate functions, so you can independently have control over each facet.

For the help of new admins, here's the basic email problem:
 Step 1: ALL emails have the same path -- User A sends a message to his configured server (Server A), which examines the destination address for a domain. Server A then uses the DNS MX record for the domain of the recipient(s) to send the message to the appropriate server(s) (Server B). The final step, is that the recipient retrieves the message from their server, Server B.
 The confusing part is that we allocate SMTP (port 25) for ALL but the last step (recipient retrieving the message). So, Server A is left to listen on a single PUBLIC port (25) for: a) messages from users who want to send messages to other local users; b) messages from users who want to send messages to other remote (non-local domain) users; c) messages from non-users who want to send messages to users; and d) messages from non-users to other non-users.

Sendmail is the "granddaddy" of mail servers -- and it is a BITCH to learn. (Learning Tree International used to have an entire 4-day (7 course-hours a day) course solely for configuring and managing sendmail.

The reason some people don't like QMail is that it follows the original theory of UNIX: each program should do ONE thing, and do it well. As I mentioned above, being an email server is not just ONE thing! So there are separate programs (this is a partial list!):
 qmail-send sends messages through one of two programs:
   qmail-local delivers messages on-site
   qmail-remote delivers messages off-site
 qmail-smtp accepts messages for delivery (usually port 25)

Now here's the key -- there can be MORE THAN ONE qmail-smtp program that can use different rules. So, for example, I can configure one qmail-smtp to listen to port 25 & perform all sorts of SPAM and AV checking, but another on another port (like 587) that REQUIRES AUTH (a login) and then does no SPAM checking (assumes a valid login is a local user -- not a SPAMMER). (I even use a different port - 465 - that REQUIRES both SSL and AUTH -- this is how MY users send e-mail!)

What confuses most people about QMAIL is that it doesn't COME with AV or SPAM controls -- they're all 3rd-party add-ons.

If you'd like a "complete package", I suggest you look into the QMail Toaster project (qmailtoaster.org). There's even an ISO image of a complete e-mail server & a virtual-server edition!

I hope this helps.... someone!


Admin to more than 30 QMail installations! (Switched from SendMail in 2004!)
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Assisted Solution

gheist earned 760 total points
ID: 22753268
Switched from Sendmail to exim in 2002... I understand exim is monolithic, but it has carefully crafted AV scanning interface, MIME parser and many other things. It has human readable (and editable without alien help) config file. I understand I might switch to postfix or qmail some other day when exim does not cope with the load.

Problem is that monolithic software (think sendmail or exim) has hard time to limit output per host. i.e when you get rejection on 10th connection they assume host is down for 30 minutes, qmail or postfix will well adapt to this situation.

It is not the problem unless you actually send such a heap of mail regularly.

Let me suggest exim for learning as its config file quite well follows mail processing in server starting with incoming smtp and ending with final delivery.
There is one bug in default config file and if you fix that it works perfectly:
LVL 21

Assisted Solution

by:Daniel McAllister
Daniel McAllister earned 920 total points
ID: 22753947
Well, I'll put in my final 2-cents worth here -- picking a mail server is very much like picking a distribution: everyone has an opinion, and everyone who disagrees with you is either a) stuipd, b) uninformed, or c) has some ulterior (eg: evil) motive.

IMHO, a mail server is just a tool, just like a screwdriver: I don't care if you like craftsman, snap-on, or riobi... just use it correctly & get the job done! (NOTE: I support over 30 mail servers for clients. MOST are QMail Toaster, 2 are "bare" QMail, 4 are PostFix, and 6 are still using SendMail. I don't tell my clients what to run, I just KEEP it running!)

So, my last 2-cent's worth? QMail Toaster (which I recommended above) does not directly support OpenBSD (there are no build scripts for ANY BSD branch)... however, one will be in the works in about 3-6 months. How do I know this? I'm one of the people making it happen.

If you're running Fedora, CentOS, Mandriva, or SUSE... the existing scripts (qmailtoaster.org) work well. Oh, and QMail Toaster comes (by default) integrated with:
 - DomainKeys, SPF, & SRS all enabled (and configured)
 - SpamAssassin, ClamAV, & Simscan
 - SquirrelMail web-based e-mail access
 - a web-based configuration tool
 - a MySQL backend for enhanced support of virtual domains & users
 - standard & SSL versions of POP & IMAP servers

That's why they call it a toaster -- it's the whole shebang all in one!

I'm now getting off my soap-box. I hereby promise to campaign no more (at least on this thread).

Good luck to the poster! Regardless of the tool used, email is one of the most challenging aspects of system admin!

I hope this helps.... someone!


Author Closing Comment

ID: 31504908
Thanks your advice.

Author Comment

ID: 22873485
Hm....i can simple to Comparison between qmail and postfix.
They can be  support Linux/Unix Server OS,but they aren't support windows OS.Postfix used SMTPand Qmail used SMTP, POP3.
Any way if i need to choose the mail system from opensource, i will choose qmail.although it have experience maintenance, or no more Incomplete document and clear examples and through the thirst party used the windows/web Clients mail access.But compare with postfix.i would choose the qmail.

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