My company wants to migrate the current mail server into a Cloud Server Provider. The Provider is the IaaS (Infrastructure as a Service) kind, not SaaS (Software as a Service). That means I have to install the OS + MTA myself.

I'd really appreciate it if you can give me a guidance, pro/con analysis, experience, etc. on the following combinations:

  • Exim on Linux
  • Postfix on Linux
  • Exim on FreeBSD
  • Postfix on FreeBSD
  • (other MTA)* on Linux/FreeBSD

*Please do not suggest sendmail and/or qmail.

Thank you all for your kind assistance.

PS: When I've made my choice, I'll change the question title to '[Solved]' and post my choice.

  • 1
    It's kind of disappointing that there are no real flashed out answers. Most people just said "Well don't do it yourself. Use this suite, use that cloud service." Hope someone with skill reads this comment and still adds some more detailed information.
    – erikbstack
    Aug 25, 2013 at 22:00
  • 2
    @erikb85 Email is hard. It took me years to become an intermediate level email admin. Learning email is much harder than learning things like web servers. It's not worth it to most people. That being said, the problem is this is a terrible question. It's like asking which is better: Toyota or Honda. And if the OP is asking about Linux vs FreeBSD, a paid service would be the best option given the implied skill level.
    – user38810
    Mar 22, 2015 at 19:37
  • Yeah that might be. But that's strange in my eyes. Email itself is such a simple protocol and what people do with it is also rather simple. Why is there no tooling that allows reasonable defaults (which I suppose would be what is needed to be useful to unskilled admins).
    – erikbstack
    Mar 23, 2015 at 16:28

6 Answers 6


If you intend to make it a dedicated mail server, I absolutely suggest Zimbra Community Edition. It is a complete mail server solution suite, including imap4, pop3, IM, webmail gui, document sharing, calendar, directory service etc. It is based on postfix for mta.

It takes 5 minutes tops to install and has a very cool and complete web administration interface. Good documentation and support through their wiki and forums sites.

  • hmm... that's an interesting alternative... I'll check it out. Thanks!
    – pepoluan
    Mar 18, 2011 at 14:27

my vote goes to debian stable and exim4 -- stable, well-documented, and lightweight (you can, of course, use postfix on debian, but exim4 is the default MTA).

Here's the canonical documentation, for reference :)

  • Aren't Debian Stable... um, too stable?
    – pepoluan
    Mar 12, 2011 at 3:51
  • @pepoluan: absolutely no such thing as too stable here. We're talking about MTAs -- it's hardly the bleeding edge of innovation. Any of these solutions will have all the functionality you need, so your decision should probably be based on stability, resource usage, and ease of management (inc. quality of documentation). In my opinion, debian stable (note that that's debian 6 squeeze as of Feb. 2011) and exim4 comes out best overall.
    – simon
    Mar 12, 2011 at 4:15
  • thanks! i don't really follow Debian, so Squeeze is out is truly news to me. And you do have a point re: MTA not bleeding edge.
    – pepoluan
    Mar 12, 2011 at 4:20

I'd steer you away from Gentoo as a server OS, simply because it's not exactly known as a stable platform with rigorous testing. If you want to use Linux, try one of the long-term support options from Ubuntu, Debian, CentOS, RHEL or SuSE.

FreeBSD has postfix and exim in ports, although it has sendmail as it's default MTA so you'll find most of the MTA documentation for FreeBSD focuses mostly on Sendmail, but that doesn't mean that it's impossible to use Exim or Postfix.

Also, be careful about your Cloud service provider. I've heard nightmares of people setting up a server in the Cloud only to find the entire IP subnet blacklisted by popular DNS blacklists because the cloud provider also has customers who send spam.

  • thanks for the warning about Gentoo's, um, non-stable-ness. I was aiming for as lightweight Linux as possible. As for the Cloud Provider, I know their people personally, and I know they proactively kicks out spam-generators from their servers.
    – pepoluan
    Mar 11, 2011 at 14:52

You don't say what your company's current mail server solution is nor whether you need to achieve any from of compatibility, so we'll assume your needs can be satisfied with the standard components. You don't mention what your mail retrieval requirements are (for example POP, IMAP, MAPI), so we'll assume IMAP. You don't specify a requirement for webmail, so we won't discuss it here but you will be able to integrate one or more of the many solutions easily with the IMAP support.

Regarding the OS, unless you have an existing support team with Linux or FreeBSD experience your choice should be a pragmatic one, based on that which you have most experience and the ease with which you can obtain support or help if you have problems. Do you need a support contract with the OS? These should be the practical considerations which will help you determine your final choice because they will ultimately be more important than the differences between the OS's. If you will be the sole supporter and have little experience with both, I would recommend the latest stable Debian Linux because it is well-documented and is straightforward to get advice for common configurations of OS, mail server, IMAP server and firewall.

The choice of MTA is less clear and is often dictated by the available experience and recommendations from friends. Exim4 and Postfix do the same thing in slightly different ways. They're both well-supported, have similar features and are actively being developed which ensures that bugs and security advisories are responded to. From my own experience, Exim4 has sufficient configuration options to be able to support all but the most esoteric requirements. It's the default MTA for Debian and has excellent support from within Debian for the supplied Debian Exim configuration utility, and outside from the extensive documentation and mailing lists.

There's no substitute for hands-on experience, so I would strongly recommend setting up some local virtual machines to perform basic installations of OS and MTA. Once you've done this, you'll discover what questions remain unanswered, based on your setup requirements. It will also give you an opportunity to experience and configure related software, for encrypting mail transfers, for authentication, for spam and virus filtering and for general server security and backup options.


I like CentOS and the Courier suite for this. Courier provides the whole shebang, inlcuding IMAP server (assuming you will have clients). A a good set of tools. Also combine it with Spamassassin.

  • Hmmm... IMO CentOS is a bit too-behind the cutting edge... but thanks for the consideration of Courier :)
    – pepoluan
    Mar 18, 2011 at 13:21
  • @pepoluan - I'm new to Linux and am reading everything I can find. Why do you say CentOS is behind? PS - I'm considering CentOS + Sendmail Sep 6, 2012 at 4:10
  • @makerofthings CentOS rarely adopt the latest version of packages; they usually wait until a package is stable before deploying. Good for stability, but if one needs the features that exist only in the latest version of a package... he/she has to wait until the package has been vetted by Red Hat and/or the CentOS team. My company's relatively small, and we need the features, and we can live with some disruptions of the mail system, so CentOS is not suitable.
    – pepoluan
    Sep 6, 2012 at 8:17
  • @pepoluan True, but you can also make your own RPMs and install them. Courier works for me, and can be made into RPMs that install on CentOS. But the main point here is Courier, not the OS/distro that it runs on. What extra "cutting edge" OS features do you need on a dedicated mail server?
    – Keith
    Sep 6, 2012 at 10:44
  • @Keith true, but if I do that then I end up with two maintenance things: Maintain the RPM, and maintain the configuration of the installed package. The "cutting edge" features for example is Postfix's pseudo-greylisting ability, which -- IIRC, at the time of my question -- exists only in the latest Postfix version, not in the version contained in CentOS. (Postfix here is just an example)
    – pepoluan
    Sep 6, 2012 at 11:28

I would suggest that you consider:

  • Cyrus Murder, which enables to share the entire IMAP mailbox namespace, but distribute the load amongst a pool of servers, and
  • FreeBSD, which is a robust system used by many companies over the world, even by Micro$oft.

I love the way FreeBSD ports mechanism greatly simplifies your everyday life, see Update your FreeBSD software with care. It's a well-documented system.

I imagine Cyrus+FreeBSD based cluster, backed by ZFS (also, on FreeBSD.org wiki), the latter being actively ported/developed by FreeBSD project.

  • I can't cluster, the Cloud I'm using has not enough resource for clustering :(
    – pepoluan
    Mar 18, 2011 at 13:20

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