Apple 10.6 manual Local Delivery Agent, Dovecot, Internet Message Access Protocol Imap

Local Delivery Agent

Mail is transferred from incoming mail storage to the mail recipient’s inbox by a local delivery agent (LDA). The LDA handles local delivery, making mail accessible by the user’s mail application. Two protocols are available from the Mac OS X Server LDA: POP and IMAP.

Mac OS X Server uses Dovecot to provide POP and IMAP service. Your mail users will set their mail application’s incoming mail server to your Mac OS X Server running Dovecot.

More information about Dovecot can be found at: http://www.dovecot.org/.

Dovecot

Dovecot is an open-source enterprise mail system for use in small to large enterprise environments. Dovecot developers have focused on security, scalability, and ease of administration.

Each message is stored as a separate file in a mail folder for each user. This design gives the server advantages in efficiency, scalability, and administration. User access to mail is primarily through software using IMAP or POP3.

Dovecot uses the configuration file /etc/dovecot/dovecot.conf. Server Admin uses the defaults file /etc/dovecot/dovecot.conf.default. Dovecot logs its events in /var/log/mailaccess.log. The Dovecot mail store is located in /var/imap/ and user folders are located in /var/spool/imap/.

The Dovecot delivery application receives mail from the Postfix delivery agent and stores the mail in user spool files in /var/spool/imap/dovecot/mail/GUID, where GUID is the Globally Unique ID (GUID) of the mail user. The user can then use IMAP or POP to retrieve messages.

After receiving mail from external MTAs, you can apply virus filtering or junk mail filtering to the messages. Mac OS X Server uses ClamAV and Spam Assassin for these tasks. For more information on enabling these, see “Limiting Junk Mail and Viruses” on page 34.

For more information about Dovecot, see http://www.dovecot.org/.

Internet Message Access Protocol (IMAP)

IMAP is the solution for people who use more than one computer to receive mail. IMAP is a client-server mail protocol that allows users to access mail from anywhere on the Internet.

With IMAP, a user’s mail is delivered to the server and stored in a remote mailbox on the server. To users, mail appears as if it were on the local computer.

A key difference between IMAP and POP is that with IMAP the mail isn’t removed from the server until the user deletes it.

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Chapter 1    Understanding Mail Service