The latest stable and current release of the cyrus-imapd server is 2.3.16 which includes support for replicated mailboxes, unified murder configuration, delayed expunge, separate metadata partitions, Sieve extensions, and much more. It requires SASLv2. For specifics about the changes refer to http://cyrusimap.web.cmu.edu/imapd/changes.html. If you are using SQL detection, some changes may be required (http://cyrusimap.web.cmu.edu/imapd/install-upgrade.html).
5.4.2. dovecot
dovecot has been upgraded to 1.2.11. In earlier versions, some very large headers were sent which could result in a denial of service. This update fixes that problem, in addition to some security improvements. Details can be found at http://dovecot.org/doc/NEWS. (Note that Fedora 12 included version 1.2.6).
sendmail has been updated to 8.14.4. There are a number of bug fixes, including some security improvements.
5.4.5. Zarafa Open Source edition
Zarafa Open Source edition is a groupware suite that is new to Fedora. It provides integration with existing Linux mail servers and uses Ajax to create a user interface that is intuitive to users of Microsoft Outlook. Zarafa Open Source edition includes an IMAP4 and a POP3 gateway as well as an iCal/CalDAV gateway. It combines a high degree of usability with the stability and flexibility of a Linux server.