Chapter 22. Mail Services

Mail is perhaps the most consistently business-critical Internet application in use today. There are few enterprises that do not rely on it, at the very least leveraging it as a primary communication medium. This popularity, though, also lends itself to exposure—and in the case of mail services, exposure has meant abuse. Fighting spam (unsolicited mail messages) and mail-based worms and viruses now accounts for some of the largest IT expenditures yearly.


Email is amazingly popular—so much that it can probably be called the killer app of the Internet age thus far. This is most likely due to its familiar paradigm. It doesn’t take much of an intellectual leap to understand the sending of a message—even a multimedia message—to someone else. It’s something that humanity has been doing for a long time, and contrasted with the Web or online chat forums, it is a very novice-friendly concept. This simplicity, though, is only skin-deep—the sending of a message from one user to another actually employs a number of systems and services that must work together.

In versions leading up to Panther, Mac OS X Server used AppleMailService, a workgroup mail server that was ported to Mac OS X from Mac OS 9 and AppleShare IP. While easy to maintain and configure, it didn’t scale to large deployments. Perhaps more important, though, was its feature set. In recent years, a number of open source spam- and virus-checking solutions have come to dominate that marketplace. AppleMailService, ...

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