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.

Homepage:
https://www.courier-mta.org/imap/
