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While the mechanics of these three tasks are specific to Cyrus IMAP, the principles
and goals behind them are the same whether you run Cyrus, Courier IMAP, or an
entirely different MDA service.
Note that in these procedures and examples, I’ll assume that you’ve already got a
working LDAP server and already know how to generate X.509 certificates. For more
information on LDAP and digital certificates, see Chapters 5 and 7.
Which IMAP Server?
The first choice an email administrator must make in building an IMAP system is
which server to use. What are the major differences between UW IMAP, Courier
IMAP, and Cyrus IMAP? In brief:
• Of the three, UW IMAP is the least flexible, as it supports only local-user-account
mail-file delivery; each local user’s inbox is stored as a single flat file—e.g., /var/
mail/myusername. This has two disadvantages: each mail user must also be a sys-
tem user, and only one process may write to any given user’s inbox at any given
time, potentially resulting in file-locking complications
• Courier IMAP, actually part of the Courier Mail Server, was designed to support
qmail’s maildir system, whereby each user has her own mail directory in which
messages are stored as individual files (which is better both from a performance
standpoint and ...