There are a few ways to resolve the issue: One option is to remove the recent update that has been pushed out by Microsoft to Outlook 2013 and Office 365 users.
Anand Khanse is the Admin of The Windows Club.com, a 10-year Microsoft MVP Awardee in Windows (2006-16) & a Windows Insider MVP.
Please read the entire post & the comments first, create a System Restore Point before making any changes to your system & be careful about any 3rd-party offers while installing freeware.
It has come to our attention that many Outlook 2013 and Office 365 users are having issues within synchronizing IMAP folders recently.
1] Run Microsoft Outlook in Safe Mode, without add-ins.
To do this, open Run box from the Win X Menu, type and hit Enter.