See: Uninstalling Outlook or Office updatesand: Uninstall Office 365 Click-To-Run Updates Important!Be aware that you will be uninstalling a security update, so only use it as a last resort and post in the Outlook Forum for additional help or contact Microsoft Support in your country via email or by phone.
This also includes your Calendar and Contacts folder when they are stored within the ost-file of your IMAP account.
To prevent this, you can change your configuration of Outlook 2013 in such a way that it behaves like Outlook 2010 and previous where the Calendar and Contacts folder were stored in a separate pst-file and thus fully recoverable.
“ Actually, the November update for Outlook 2013 (KB2837618) fixes a whole lot of IMAP issues and is highly recommended.
Amongst others, the update makes sure that IMAP accounts will not repeatedly completely resynch folders, will not create duplicates of default folders, will more reliably map the special server folders and make it less likely that folders will get marked as “This computer only”.
Before emptying the cache, you may want to ensure that your Outlook information is backed up.