Courier-IMAP is a server that provides IMAP access to maildirs. This IMAP server does NOT handle traditional mailbox files (/var/spool/mail, and derivatives), it was written for the specific purpose of providing IMAP access to maildirs. "Maildir" is a directory-based mail storage format originally introduced in the Qmail mail server, and adopted as an alternative mail storage format by both Exim and Postfix. Courier-IMAP is popular on Qmail/Exim/Postfix sites that are configured to use maildirs. The primary advantage of maildirs is that multiple applications can access the same maildir simultaneously without requiring any kind of locking whatsoever. It is a faster and more efficient way to store mail. It works particularly well over NFS, which has a long history of locking-related woes. This package differs from a vanilla Courier-IMAP installation in that the files are installed at locations that more closely correspond to a Courier installation.