Mail server

A Mail server is a computer server which provides SMTP, POP3 and/or IMAP services. This enables the sending and receiving of email messages.

There are several programs that run on mail servers: SMTP

• Sendmail - The most versatile, but the one with the most cryptic configuration file. It has had a history of security holes, including the Morris worm.
• Postfix[?] - By Wietse venema[?]. This MTA is designed for security, with several separate programs each of which does a task.
• qmail - By Dan Bernstein. Similar in design to Postfix. Additionally the programs run as different user IDs.
• Exim
• Courier

POP/IMAP

• UW IMAP - Uses mbox format.
• Courier IMAP - Uses Maildir format, which is much faster and requires no file locking.

Mail filtering

• Procmail - A general-purpose mail-sorting program.
• Vipul's Razor - By Vipul Ved Prakash[?]. Razor users (which may be spamtraps) report spam to Razor; mail servers ask Razor whether incoming messages are spam.
• SpamAssassin - Uses several criteria, including Razor, to recognize spam.