From Howto Forge:

In this how to I will explain how to setup a Postfix virtual mailserver with Courier-IMAP, Maildrop and Postfix Admin GUI. We will secure our mailserver with Mailscanner and Clamav as anti-virus and Spamassassin as anti-spam.

Read the full thing at http://www.howtoforge.com/virtual_users_postfix_courier_mailscanner_clamav_centos

From arstechnica:

Years removed from the original release of Postfix, the Unix-based mail server is still serving oodles of people every day. As a great alternative to Microsoft Exchange and one of the many nephews of crazy uncle Sendmail, Postfix rapidly becoming a major player amongst Linux mail servers. Sendmail still gets a lot of love in the Linux community, but Postfix is a much simpler setup, and good for users who do not want to spend a lot of time configuring a mail server. Postfix provides core e-mail functionality with very little effort.

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From Newsforge:

Like many things in the Unix, GNU, and BSD worlds, the Postfix mail transport agent (MTA) is powerful but difficult to configure optimally. With basic instructions and a couple of hours (or more) to test the configuration, you can probably make Postfix work, but how do you make it work to its full potential? How do you make it more secure? How do you make it get rid of spam? How do you configure it for complex situations that involve multiple servers, email addresses, email groups, and domains? That's what "The Book of Postfix" is for.

Read the full review here

From Newsforge:

Postfix is fast out of the box, but like other packages, you can usually tune it to work even faster. Furthermore, there are situations where Postfix may not perform as well as you expected, whether because of hardware or software limitations on the server system or other adverse conditions, such as a big influx of spam or undeliverable mail. This article shows you how to find and analyze the most common performance problem.

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From Newsforge:

Last time we talked about how to get a simple installation of Postfix up and running. Once your organization becomes relatively complex, you will find yourself wanting to do things with email that may not seem immediately important. The first and most important thing is, of course, that the mail flows and that you can send and receive. I'm willing to bet that the first enhancement that comes to mind for people is spam control, or unsolicited commercial email (UCE). But that, as they say, is just the beginning. On that note, I'm going to save the best for last -- or is it the worst?

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From Linux Journal:

Postfix: The Definitive Guide is a beautifully written book about a beautifully designed program. Kyle Dent's writing is precise and concise without being too dense to read--standards, for example, typically are precise and dense. After the first chapter or two, I asked, "Has this guy written anything else?" Answer: the Postfix section of Running Linux, 4th Ed.

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