Lots of fixes since 2.2.alpha1, especially related to dsync. Also dsync now supports syncing private message flags when INDEXPVT is used.
Here’s again the list of all the major changes in v2.2:
* When creating home directories, the permissions are copied from the parent directory if it has setgid-bit set. For full details, see [wiki2.dovecot.org/SharedMailboxes/Permissions](http://wiki2.dovecot.org/SharedMailboxes/Permissions) * "doveadm auth" command was renamed to "doveadm auth test" * IMAP: ID command now advertises server name as Dovecot by default. It was already trivial to guess this from command replies. * dovecot.index.cache files can be safely accessed only by v2.1.11+. Older versions may think they're corrupted and delete them. + Implemented IMAP MOVE and BINARY extensions + Implemented IMAP CATENATE, URLAUTH and URLAUTH=BINARY extensions (by Stephan Bosch). + Implemented IMAP NOTIFY extension. Requires mailbox_list_index=yes to be enabled. + Redesigned and rewritten dsync. The new design makes the syncing faster, more reliable and more featureful. The new dsync protocol isn't backwards compatible with old dsync versions (but is designed to be forwards compatible with future versions). + All mailbox formats now support per-user message flags for shared mailboxes by using a private index. It can be enabled by adding :INDEXPVT=<path> to mail location. This should be used instead of :INDEX also for Maildir/mbox to improve performance. + Improved mailbox list indexes. They should be usable now, although still disabled by default. + Added LAYOUT=index. The mailbox directories are created using their GUIDs in the filesystem, while the actual GUID <-> name mapping exists only in the index. + LMTP proxy: Implemented XCLIENT extension for passing remote IP address through proxy.