What is best for a Personal/SMB mail server running on an Ubuntu Server (8.04+)?
I want to setup my own mail server at home to evaluate some options for my company before I make a recommendation. Which is the most secure, efficient, and reliable? Also, which is easiest to integrate with an LDAP and Calendar solution?
I've personally have worked extensively with MS-Exchange, Courier and Cyrus and, to much lesser degree, Dovecot.
I can say, without a doubt, that Cyrus is my most preferred choice. Back to the original question, any one of these will work fine for small email install base. Small, I mean, probably less than 1,000 mailboxes and less than 1,000 concurrent IMAP/POP connections. Other factors like mail volume play an important role too..
We stood up Email system years ago for our own internal use based on Courier. We're an IT consulting company. Over the years we began taking on hosting of our customer's email as well as selling an EMail appliance comprised of our assemblance of open source projects and management scripts...
About 3-4 years into it, we dumped Courier for Cyrus. We also dumped Sendmail for Postfix. We did an extensive study of all the open source and commercial options at the time and settled on Cyrus.
Totally agree that Cyrus is the most difficult to grasp but I would not characterize it as very non-standard and that being the reason for its difficult understanding. It's difficult because most documentation on the web is out grossly dated and sparse so it takes a lot of digging to get answers. Cyrus, on the contrary, is very RFC obdient. I use to have to figure out why Cyrus seemed broken and found that in most cases it was merely following the standards to the T so well that you soon figure that most everything else is broken instead. As example, I once had to look into a problem where a customer claimed email was bouncing but the email address was correct. Using Outlook, Outlook has this nasty bug where it would capitalized the first letter in an email address. Per the RFCs, all email addresses are lowercase. If you mix cases, you will find many email systems will silently correct for this.
As for performance: Cyrus, in my experience, has the best options that I don't see in the others. Specifically, you can add more front-end IMAP4/POP3 proxy servers or backend servers to distribute load where needed. This allows you to scale in terms of both concurrent connections (add more front ends) as well as storage and mailbox deliver/retrival traffic (add more backends).
Last time I checked, neither Dovecot nor Courier supported these options.
Microsoft Exchange 2010, recently released, is now introducing distributed & replicated mailbox stores so they are playing a bit of catchup in this category.
Dovecot is the modern choice for a fast, lightweight IMAP server that supports SSL and LDAP easily. It supports a whole lot of load faster and more efficiently than Courier or Cyrus and uses traditional Maildir - our Dovecot runs like a champ and is utterly reliable.
If you want a full Exchange solution what you want is to engage a product that has already done this, as it's no easy task -- in most if not all of the real solutions the clients must install a custom plugin in Outlook. Take a look at http://www.zimbra.com/ for one of the most popular solutions out there.
Dovecot works fine for me; Courier is a little creaky, and Cyrus has one too many non-standardnesses (mostly in it's storage format) for me to be completely comfortable with it. All will integrate with LDAP easily enough; if you're trying to roll your IMAP server into your calendar, though, you're doing it wrong.
Few years ago, before switching to Google Apps, I used Cyrus because it was the most feature complete having shared-folders. These are very useful for small businesses because it does enable you to share emails by dragging them from one folder to another.
I don't know if nowdays the others have this feature but I can confirm that Cyrus administration is a real pain. Maybe there are some distributions that have a web interface for that but I'm now aware of them.
Since you mention calendar as well, I'd have to mention "radicale". It a CalDAV server, lightweight, works, and easy-to-configure. CalDAV is supported everywhere nowadays, so you shouldn't have any issues.
