If you are not able to avoid this issue then update it, you will get further steps for fixing this issue temporarily. If you are also planning to try this new update then please avoid the update for a while until Microsoft provides fixes for the bugs.
The main reason behind IMAP folders not syncing in Outlook is security update (KB2837618 or KB2837643).
What Are The Causes Of IMAP Sync Issues With Outlook? This happens in all hosts due to recent updates that Microsoft has pushed out for all its users. Many of the Outlook 2013 and Office 365 users are getting issues while synchronizing their IMAP folders recently. With the help of this, you can set up the multiple email accounts on Outlook for accessing your mailboxes right from the desktop. MS Outlook supports IMAP/POP3 and Exchange accounts that help you to enable the configuration of your Gmail, Yahoo! Mail, AOL, Exchange, and other email accounts. Microsoft Outlook 2013 is the latest version of Microsoft Outlook is the component of MS Office suite and the most preferred email client across the globe.
