There are a lot of mail servers out there. Microsoft Exchange has been the dominant corporate mail server in the enterprise on Windows, but I've been using Kerio Mailserver for a long time now and am still wondering if there aren't any better solutions.
Which mail-server do you use, and why?
What feature make a specific mail-server 'stand out'?
Both *NIX and Windows applications are welcome.
Postfix ... and for the why http://www.redhat.com/support/resources/howto/RH-postfix-HOWTO/c49.html
Exim + Exchange.
Exchange is a pretty good groupware client, and advantage No.1[*] is Activesync (email + calendar sync) which frees us from relying on Blackberry :)
Having said that, I wouldn't make an exchange server directly internet facing as the bulk of mail received by a normal corporate MTA is invalid (spam etc) and the cost per message of running an efficient exchange server is much higher that a solid *nix based MTA.
Exim is (IMHO, and as mentioned) the most flexible, stable and resource efficient way of handling large or small volumes of email - you can have spam/virus filtering with a few additional apps and any rules based flexibility required using the exim filter system. I have never come across a mail requirement that couldn't be handled by exim (and I've had some strange requirements) and the documentation and mailing list support is great.
My usual setup is Internet -> Exim -> internal Exchange server with a bit of NAT for active sync and outlook web access. Scalable, secure & easy to manage.
[*] for me. I think other people like it for other reasons... :)
Ubuntu 8.04 server + Postfix + Dovecot. IMAP clients. Reason is KISS. Easy to set up and care+feeding is minimal. Modest hardware requirements.
We use Zimbra. It's much cheaper than Exchange, uses open source technologies, the Desktop client works on Windows, Linux and Non-PPC Mac's.
The server portion is also a very easy install on a Debian box, but runs on Windows as well.
I'm currently using hMailServer to host email for 5 different domains.
I'm using SquirrelMail to provide webmail to those domains.
This is running on a Windows 2003 R2 box with IIS6 to serve the webmail. The main reasons I'm running this combination is because both programs are free, and don't need calendaring at this time. These are also relatively painless for somebody that has only done Windows.
My company uses Exchange for collaboration, but I made them use Exim for the gateways. Exim is the most flexible mail server I've ever seen and is a joy to use and I couldn't imagine trying to do some of the things I'm asked to do with only Exchange (domain filtering based on regexp, normalizing domains so that our users in exchange only have one domain and our 20 public domains still work, handling the fact that at the moment a given lp@domain can exist in three different platforms (legacy-linux, Lotus, and Exchange), etc)
I'm using the free version (up to 10 users) of SmarterMail. Pretty full-featured w/ built-in ClamAV and SpamAssasin. It also has calendaring, web-mail, groups, etc.
Exim throughout. Why?
I've had to use sendmail and qmail heavily in the past. And still today, occasionally. Both of which prove only to cause me immense pain whenever our paths cross.
Groupwise. It takes only one sysadmin (me) to support mailboxes for 7000 people. Server-side I think is great. Client-side is... getting better.
Groupwise. Server-side has been ROCK SOLID since the switch to OES, which is basically SLES. The client is natively 'cross-platform' (*nix/Mac one is Java), so if you're in a Mac/Windows/Linux environment, you don't have to force people to have a Windows desktop or struggle with the horrible outlook web access client when not using Internet Explorer.
Groupwise Web Access, Mobile clients, etc. don't take a PHD and 3 years of training on a high mountain in Washington State to deploy... unlike OWA via HTTPS.
Overall, it's still a bit of an odd duck, but it's really nice to have an enterprise mail platform that you can put up and run without a headache.
Postfix if you are running mail yourself. It's a bit of work to setup but a joy to use once it's working.
For hosted email, going with Google Apps works just fine.
We're primarily a Windows shop, but like the OP, we use Kerio Mailserver instead of Exchange for our internal groupware needs.
Our websites send out a ton of email. All this email and even email from our corporate Kerio server are sent via a mailhub running Postfix.
MailEnable is like $200, works great if you don't need the exchange features
I can't say enough good about SmarterMail: http://www.smartertools.com/SmarterMail/Features/Windows-Mail-Server-Software-Webmail-Exchange-Alternative.aspx
My experience with the app has been solid. We use for it client mail hosting. We host about 200+ clients, 1000+ users, and plus a number of SMTP gateways. It's pretty flexible as well.
And for small business with under 10 users, it's free: http://www.smartertools.com/SmarterMail/Compare-Mail-Server-Editions.aspx
communigate - but with it's shoddy iPhone integration, I am beginning to wish we didn't
I used Sendmail for many years. However, when I needed to overcome my ISP's mail size limit, i.e. the size of an individual email, I started using a commercial relay service. The commercial relay service requires authentication each time you send email. At the time, and it may still be true I don't know, Sendmail did not support this. Consequently, I needed a secure MTA that did support this mechanism and that turned out to be Postfix. I've now used Postfix for several years and it's worked great. It was easy to setup, at least compared to Sendmail, and it doesn't need the same number of updates to keep it secure as Sendmail did, i.e. it's pretty stable and secure.
I switched our email to Google Apps for Domains back in mid '07 and never looked back. It's been fantastic for blocking spam. I even pretty must have everyone using it through the web and not a desktop client, I only have one hold out who insists on using Outlook. I've found it really useful for online collaboration tools & sharing documents & calendar events.
I've used sendmail, qmail, and exim. Of those I prefer exim, though qmail is ok though I remember administration to be frustrating. I try to avoid sendmail as much as possible.
If I were looking to set up a new mail server today I would look to exim, exchange, and gmail for your domain, depending on the particular use case. I used to host my own personal mail but now I just use gmail (the spam filtering and pervasive availability is a big win).
Exchange 2007, it's a hog to run and administrate, even with Powershell, but the user-experience is as usual hard to match (especially with easy-to-manage Server Activesync support for all kinds of mobile devices).
The 2007 version is more modular and supports thinner gateway roles which could reduce some of the resource hoginess I guess, mitigating some or all needs for alternate front-end mail servers...
Facing the internet through Microsoft ISA 2006 for the moment - I kinda love that thing for some reason. It's like, a robust firewall with good application layer filtering, easy SSL bridging, with a simple to use interface, that supports easy clustering. And it's from Microsoft... it's kinda hard to believe actually, I have to poke at it regularly just to see that it's real. There's a newer version out there, renamed into the Forefront namespace these days I think, Threat Management Gateway or something annoying like that.
First 3 years, Sendmail + Amavis (shell-script version). I did a tiny mod to the script to trap attachments by extension.
Last 7 years, Postfix + Amavis, and in the last 3-4 years, Dovecot. Tight, well-integrated. Catches better than 90% spam on first pass, catches 100% of malware on first pass. Dovecot provides speedy access to mailboxes via IMAP - largest box is low-5-digits and loads in less than 5 seconds.
We're adding a single in-house Exchange server this year, probably completing the transition in 2-3 months. The Postfix setup will continue to function as a scanning gateway, and provide IMAP access to Exchange (via Dovecot's proxy features) from the outside.
At work, all google apps. Cheap, hosted somewhat reliably and nice and feature-y.
At home, postfix + dovecot.
I use Courier. It can certainly handle load and it's not a PITA to configure.
I used qmail for a while many years back. It was an interesting learning exercise, especially adding "extra" things so I could do things like local relaying. However, I rebuilt my server some while afterwards and looking at all the effort required to get qmail going again, I asked "why am I bothering?" By then, I had found Courier-IMAP to provide IMAP access to my maildir storage and in the interim the rest of the Courier MTA had been released. It was much easier to install and much much easier to configure than qmail, so my decision was made.
I haven't tried Exim, but I had to work with Postfix at one job and was very annoyed at its complex configuration. I had to make it accept email for non-existent users and pass it to a script for our application (which handled email intermally). Postfix made this unnecessarily difficult IMO, but the sysadmin wouldn't countenance a change to another MTA.
The only wrinkle with Courier is that the cutting edge MTA tools (e.g. SPF support, grey-listing) are a bit behind everything else because of its small share. And it doesn't get on 100% with fetchmail sending to it, for some reason I couldn't figure out.
I have been using ModusMail by Vircom (for Windows) for a number of years with great success. There are two primary reasons that I use it. One is that it is an extremely feature-rich, mature product. It can integrate with just about anything else that I need, supports secure connections, and has a very, very good anti-spam solution that is constantly being updated by a dedicated team of professionals, etc. The second reason is that it requires very little maintenance. The software pretty much runs itself. We give customers access to manage their own mailboxes, we generate reports for accounting so they can bill accordingly, and hardly ever have to spend time "managing" the solution. For larger enterprises or situations where e-mail absolutely cannot go down, Vircom also offers a cluster solutions where two of them can work in tandem to ensure maximum uptime.
Now for the cons. No system is perfect, so there are bound to be some things that people won't like about any solution. For ModusMail, the first is cost. It is expensive, yes, but worth every penny in the amount of administration time we save by using it. The second is that is it proprietary software. For me this isn't much of a problem, but some people would scream bloody murder if they can't see the source code, so that is a potential issue. The other con is that is is a pure e-mail server, not a collaboration platform like Exchange. ModusMail handles e-mail via SMTP, POP, and IMAP. It ships with a webmail application which includes basic contacts, but that's about it. If you're looking for group calendaring or other collaboration functions, ModusMail is not for you.
As of this writing, ModusMail is at version 4.6, so some of the above may not apply if you're reading this after a new version is released.
I used Qmail for years - mostly because I spent a lot of time maintaining a medium-sized Qmail installation for one of my employers a few years ago.
I recently moved all my email from Qmail to Exim, and managed to (mostly) script the migration of all the virtual domains. I also moved from using Courier to Dovecot for IMAP and POP3.
http://struction.de/projects/HOWTO_VirtualMail_Exim-MySQL-Spamassassin-ClamAV-Dovecot/index?set_style=clean is a good guide on combining Exim with ClamAV, Spamassassin, Dovecot with a MySQL backend.
We use Exchange in-house, but we did use hMailServer at a customer's site where we needed a cheap (free) mail server to provide distribution groups for e-mail alerting.
Exchange 2007! Not cheap... but works. Easy. Lots of info on the net if you have problems.
Exchange, primarily so that we can have a single vendor client/server platform so that if we get any "funnies" we won't have each vendor trying to blame the other (a very important reason IMO). Single sign on is also a crucial factor.
We also have Domino available but - aside from one evangelist - the concensus is that the client is not something we would like to give to our users.
I've run Exchange 2007 at a past employer, but now we are "running" Google Apps for Domains. Much cheaper, and way better calendar sharing than Exchange.
For a Windows shop, Ipswitch's IMail packs quite a punch for the money.
Postfix+postfixadmin+dovecot and rouncube webmail (w/postfixadmin plugin), all using a MySQL backend.
Simply because it's free and rock stable.
Probably going to move to Exchange when I have the budget for it. I want to synchronize my calendar from my smartphone (our sales team -really- wants it).
I like Unison as it integrates all my communications tools in one application-very simple as you access email/im and telephone rules from one simple interface... It manager doesn't have anymore multitude of servers to manage as well telephony becomes integrated with the rest of tech tools
Our mailsystem is based around MS Exchange, as there doesn't seem to be much competition to it for the collaboration tools (ie. shared calendaring, etc.)
But beyond that we use postfix with virtualmin to allow departments to manage their own domain aliases and pop3 mailboxes.
And all of this sits behind 2 postfix / amavisd-new / spamassasin / clamav based mail filters. There is a great tutorial on setting this all up at http://www200.pair.com/mecham/spam/
I'm a qmail user. I think qmail would be a dubious choice right now, given that djb, it's author, hasn't updated the core software in years and seems uninterested in either doing so or releasing the software under a license that would allow it to be forked in useful way. (qmail's license allows patches, but not direct redistribution of modified versions. This is somewhat inconvenient).
However, I would be remiss if I didn't mention the EXCELLENT software I've used to pull together integrated qmail servers for the past several years: Matt Simerson's mail toaster. http://mail-toaster.org/
if you read about sendmail at all you quickly discover its history of "bug of the week". Other solutions have come out since then, in fact a lot.
Postfix makes a good drop in replacment.
Qmail touts its correctness and security.
I know more about SELinux than qmail so I take my chances with having the correct SELinux policy (ie custom SELinux policy, though the default should be fine, properly configured of course) with a drop in sendmail replacement.
Groupwise. Because it gives users something to complain about. That's the only reason I can think of for using it.
