We have a computer running Windows 7 SP1 and all latest updates as well as Microsoft Office 2013 also with all updates. Last week Outlook stopped synching with IMAP which is hosted on a Linux mail server.
Other devices and applications (Thunderbird, Live Mail, iPhone) all work just fine, however Outlook simply will not sych. I have deleted the .OST file, removed the profile in Outlook and recreated it, Unsubscribed and Re-Subscribed to all the folders. None of those things seem to work.
It seems to be a recurring theme in my google searches, however no one seems to have a fix available. There was mention of security patch that might fix the problem, however I have confirmed the patch is installed and still is not working. No patches or other changes to the system were made prior to the problem starting.
I am about to conclude that Outlook 2013 is buggy and advise the user to switch to a different email client, however this client is adamant about using Outlook.