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Goodbye MS Exchange: Good Linux Email Servers
Say Good-Bye to Jabba
February 23, 2011
Don't pay top dollar for Microsoft lard when you can get the best mail servers for free. The Linux world is full of great servers, both free and with commercial support options.
In part 1 of this series I reiterated the the obvious "Linux Servers Are the Smart Business Choice". Today let's take a look at the difference between email and groupware servers, which one you should choose, and a selection of good email servers that run on Linux.
Don't Use Exchange For POP/IMAPA whole lot of shops, even very small ones, fork over big bucks for an Exchange server, which requires Active Directory, which requires one of the many versions of Windows Server (differentiated only by price and different degrees of being feature-crippled) when all they want is a simple POP/IMAP mail server. Every time you touch a Windows server you incur another license charge, and if you want actual users to connect to it you pay for those too. They really want you to buy Sharepoint too, but it's not an Exchange dependency. Yet.
Do you really need a groupware suite? The idea is to put all this shared stuff on a single server, under a single interface to enable "unified messaging and collaboration." Shared files, contacts, calendars, instant messaging, mobile messaging, chats and forums, wikis, video chat, VoIP (voice over IP), and gosh knows what else all in one giant suite. In the FOSS world you can easily find these as individual servers, or all woven together in groupware suites. If all you need is email then you don't need groupware.
There are many excellent FOSS mail servers. They have much lower hardware requirements than MS Exchange, perform considerably better, and are more reliable. They are standards-compliant so you don't have your mail stores trapped in some weird fragile binary file format, there are no hassles with silly proprietary network protocols, and your users can use any mail client they want.
Let's first review some essential terminology. Microsoft loves obscuring the important details and mangling terminology. We are skilled, precise Linux admins so we don't do that. Douglas McIlroy, inventor of Unix pipes and one of the founders of the Unix tradition, is often quoted:
"Write programs that do one thing and do it well. Write programs to work together."
For the most part Linux follows this Unix philosophy, and that is why we can mix and match anything and everything in the Linux world. This can also lead to confusion when it comes to figuring out which pieces to put together. But there is a substantial benefit to knowing all of this: you can tailor your mail server exactly to suit your needs. Here are the basic building blocks of an email system:
MTAMail (or message) transfer agent. An MTA transfers mail from one computer to another. An MTA is also called an SMTP server. Postfix, Exim, and Sendmail are popular, robust MTAs that power everything from tiny personal mail servers to giant ISPs.
MUAMail user agent, also called email client, for end users to fetch and send emails. KMail, Mutt, Balsa, Thunderbird, Thunderbird derivatives Icedove and Spicebird, Claws, Evolution, and Sylpheed are all MUAs.
SMTPSimple Mail Transfer Protocol, the networking protocol used by MTAs to transfer messages (See RFC 5321 for complete details).