One of the developing trends we've seen is sites moving out of Zimbra and into Exchange.
Imapsync is excellent for moving the email, but the calendars, tasks, and contacts are another issue.
While we've have a full-state migration solution for over a year, a lot of the folks who want to move want something simple, but still server-side, and oh, could we PLEASE keep meetings live?
It's a tall order, but as usual we deliver.
This is the basic screen:
In short what you do is export your Zimbra calendars, tasks, and contacts server-side (using either zmmailbox, cURL, or whatever you're comfortable with) in ICS and VCF format, then run this application against the resulting files.
With the proper credentials on your Exchange server (and yes, we have tested it against Office 365 and Live @ Edu), these will upload. Meetings will be re-proposed (so your users will see invitations in their inboxes come the Monday morning post-migration). The alternative is the full-blown Sumatra process which is overkill for many of you moving out of Zimbra.
Rather than our three step process (export, map user IDs in a database, and insert into Exchange), this is a TWO step process (export, import) with no intermediate mapping. So if you're changing a lot of user IDs going from Zimbra to Exchange, this is probably NOT the recommended process for you.
We're in test right now with this at a couple of sites and will let you know when it's ready for prime time. We'll give you the full documentation set and a video then too.