Extremely small footprint. On x86, the
Courier IMAP server's main
daemon is a fraction of the size of the UW-IMAP server, and
has a greatly reduced memory footprint.
Ability to restrict the maximum number
of IMAP logins, and the
maximum number of logins from the same IP address. This
will prevent denial-of-service attacks where the attacker
attempts to overload the server with multiple login
connections.
Shared folders. With additional
server-side setup, folders can be shared between groups of
accounts.
IMAP over SSL. If OpenSSL or GnuTLS is installed, the
Courier IMAP server will,
optionally, accept IMAP
connections over SSL.
The IMAP STARTTLS
extension is also implemented.
Authentication using SSL certificates.
IPv6 support, if available.
IMAP extensions that implement
server-side sorting. This can be optionally disabled in
environments that have limited resources.
The Courier IMAP server implements many
popular IMAP protocol
extensions that provide value-added functionality with most
popular IMAP
clients.
Sorting and searching in non-English
character sets. Download the source code to obtain a list
of currently supported character sets.
A compatible POP3 server is also included in the
Courier IMAP server
package, that uses the same authentication modules. The
POP3 server can only
access the INBOX, and cannot access any folders.
IMAP/POP3 proxying. It is possible to
distribute all mailboxes between multiple servers. A
separate server (or a pool of servers) accepts all
IMAP/POP3 connections, then connects to the
right server based on the mailbox the connecting client is
logging into.