I realise there are already several posts relating to Outlook 2013 and IMAP, but we're having a specific issue which I don't think is completely covered elsewhere.

I work for a department of a university, and we have quite a lot of staff using Outlook to access the main department IMAP server (which is running Cyrus) and also a server provided within the department for archive purposes (which is running dovecot).  The same issue has occurred with both servers.  It seems to occur most often when moving large folders or large numbers of emails, but it's hard to be sure.

The symptoms:

The user checks webmail or checks their mail from a different computer, and discovers that the folders and emails displayed in Outlook are not the same as those displayed on the server.  Despite the fact there are no error messages of any sort within Outlook.  Sometimes whole folders are missing in Outlook, sometimes on the server.  Sometimes folders appear in both, but do not contain the same messages.  Outlook continues to behave exactly as if it were syncing with the server, and allows you to create folders and move messages, and incoming mail still appears in the INBOX so unless you check webmail you're simply not aware of the issue.

If you remove the .ost file associated with the account and restart Outlook then Outlook recreates its local cache, and is then displaying everything correctly again, however anything which was only stored locally is lost!  For this reason we have taken to exporting all mail to a .pst first and then removing the .ost file - before opening the .pst file to retrieve the missing mail.  When you do this you discover that there are in fact very many error messages in the Sync Issues folder which were simply not being displayed in any way in Outlook previously!

I note that if you have a copy of Outlook which is in this state you can use the IMAP Folders dialog box to see all the folders and the server and it clearly shows that they are not the same as those displaying in Outlook!

This issue is sufficiently common that we're having to advise people to revert to Outlook 2010 or to use Thunderbird instead, and I am aware that at least some email has been lost - thankfully we've been able to have some of it restored from backups on the servers, but this will not always be an option when mail has been missing for longer periods.

I'm wondering if there's a good way to approach Microsoft Technical Support in order to get this taken seriously as a bug in Outlook, when we don't have a support contract with them.  Or if anyone is aware of this bug and has a better fix?

I also posted this question on answers.microsoft.com where it was suggested I try the OffCAT analyser tool, but that didn't help. See:

http://answers.microsoft.com/en-us/office/forum/office_2013_release-outlook/outlook-2013-imap-synchronisation-bug/4b040195-380b-49a7-b865-6336c03f2a14

Disappointed to have had no replies to this - and a similar post in another technet forum has been deleted without notifying me.