If it's speed and security you're looking for, Postfix is a very nominal choice for a MTA. The MTA uses multiple layers of defense to protect the local system against intruders, as well as having the ability to run in a chroot jail.
All of the many configuration parameters can be found in the main.cf file, located in the ./conf directory in the postfix source. You need not change every parameter, as they are set to sensible defaults. Here are the details on some of the more important parameters, which will affect the performance of Postfix the most. Please note that if you change the main.cf file after installation, you must issue the postfix reload command. After installation, the main.cf file can be found in the /etc/postfix directory.
News: Server Security
