Chapter 25 . Running a Mail Server 675 (Java web server)
Chapter 25 . Running a Mail Server 675 Web mail applications use IMAP as their backend protocol for accessing mailboxes; this eliminates the need for direct access to the mail files and makes it easier to split functions between systems. About the System and the Software Used The mail server configuration described in this chapter is based on the Exim mail transfer agent. Along with Exim, several other components are added for managing the server and checking e-mail contents for spam and viruses: . Exim (http://www.exim-mta.org/) is an MTA written and designed by Philip Hazel at the University of Cambridge, with contributions from many people around the world. The version referred to in this chapter includes the Exiscan-ACL patches (http://duncanthrax.net/exiscan-acl/) packages from Tom Kistner. This patch allows content scanning from within Exim. Because this patch is integrated with Exim, its features are considered part of Exim for the purpose of this chapter. . Maildrop (http://www.flounder.net/~mrsam/maildrop/) is a local MDA that is part of the Courier MTA package, but is also available as a standalone program. It is used in this configuration to allow the use of advanced features, such as mailbox quotas and server-side message sorting. . Courier IMAP and POP (http://www.courier-mta.org/imap/), like Maildrop, are parts of the Courier MTA that are also available separately. They were chosen for their easy installation, good performance, and compatibility with the Maildir format mail directories. . ClamAV (www.clamav.net) is an open source virus scanner that detects more than 20,000 viruses, worms, and Trojans. It uses a virus pattern database to identify viruses and includes a program named freshclam that handles updating the database automatically. Like SpamAssassin, ClamAV includes a daemon (clamd), a client (clamdscan), and a second command-line tool that does not use the daemon (clamscan). . SpamAssassin (http://spamassassin.apache.org/) is a spam-filtering program written in Perl. It uses a large set of rules to help determine how spammy a message looks and assigns a score based on the total of the rule values. For performance reasons, SpamAssassin uses a background daemon called spamd to perform message analysis. Access to this daemon is performed through the spamc client. A spamassassin command that performs the analysis without using spamd is also installed but is not used by either of the example configurations in this chapter.
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