We are using the latest version of Zimbra with a number of various Macs on various versions of Mac OS X. For the client software, we are using Apple Mail, set to read mail from Zimbra using IMAP.
Half of our users are having great success. Half are having issues with Apple Mail getting "stuck" while synchronizing mail with the server, and no new mail can be read or sent when this is happening (rendering the client software useless). Force quitting the Mail.app program and restarting it resolves the issue every time, but only for about 24 hours, when it happens again.
We run a large variety of desktops and laptops, running everything from Snow Leopard to Mountain Lion. There seems to be no rhyme or reason or pattern to the users that are having issues, except that they are the heaviest users of mail (ie, most number of messages stored on server). However, the issue is not always user focused, sometimes it is machine specific. That is, a user can login from Desktop machine and get all mail, but the problem occurs when the login via their Laptop - all on a repeatable basis [its not random].
If the users logs into Mail via webclient, all emails, files, and folders seem to be there, so it seems to point to an issue between Apple Mail and Zimbra, but that doesn't explain why only half my users are having problems.
I would like to find out if anyone else is having similar issues (or resolutions) to users in similar situations.