Support added for FastMail-style conversations (threaded messages). (See the conversations options in imapd.conf)
Optional Xapian integration for faster and shinier search. Note that this requires custom patches to Xapian, in this release. (See the search_engine option in imapd.conf)
Archive support has arrived! Requires addition of an archive partition. (See archive_* options in imapd.conf)
Basic JMAP support. (See httpmodules in imapd.conf)
Optional ClamAV integration for AntiVirus support is now working again. Requires separate installation of ClamAV. (See configure.ac --with-clamav=DIR)
Dropped support for Berkeley DB.
The handling of configure options has changed, dropping support for --with-cyrus-prefix and --with-service-path in favour of the more conventional --prefix, --bindir, --sbindir, and --libexecdir.
Binaries executed by the cyrus-master(8) service process are now installed to --libexecdir. Other binaries are installed to --bindir and/or --sbindir.
The make installbinsymlinks target can be used to set up symlinks to everything in --bindir, if you need that in your environment.
Lots of fixes to caldav and carddav.
Includes the addition of a new daemon (calalarmd) which periodically processes a global database containing the “next” alarm for each item, and sends the relevant mboxevents. (See configure.ac --with-calalarmd)
Replication reliability fixes.
Improved LIST-EXTENDED: more imap tests now succeed.
collectnews!:*:Tf,WO:collectnews
This behavior can be turned off by a configuration option imapd.conf--which may be desirable because of certain clients that ask for a "mail directory" setting for IMAP which will now cause problems when it was ignored before. (The default is for the reference argument to be honored.)