Mail Server
There are several major mail servers that are important in Linux.  Sendmail is a standard that has been around a long time.  Postfix, which was written with security and speed as a focus, has moved into a position of prominence in many Linux distributions.  Exim and QMail are also alternatives that are available.
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# Article Title
1 Blocking Zombie Spam Netblocks
2 Protecting Postfix with AppArmor
3 Protect Postfix with AppArmor Templates
4 Postfix Manual
5 Protect Postfix From Attack
6 Mobile Users with Postfix
7 Postfix Mail Statistics
8 Postfix Mail Server Course
9 Postfix Mail Server Design
10 Postfix Mail Gateway
11 Postfix Mailbox Changes
12 Postfix SPAM Control
13 Postfix Mail Server Configuration
14 Sendmail: Basic Setup