This bug in Outlook occurs when Outlook doesn't properly test to see whether or not it should only download headers or attempt to download full messages. It looks something like this:
Task 'Synchronizing subscribed folders' reported error (0x800CCC0F) : 'Outlook cannot synchronize subscribed folders for [email_address]. Error: This IMAP command cannot be sent to the server before the connection was terminated.'
To fix this issue, force Outlook to only obtain headers when synchronizing mailboxes by completing the following steps in Outlook 2010 or newer:
1. Click the Send/Receive tab
2. Click the Send/Receive Groups dropdown list
3. Select Define Send/Receive Groups...
4. Click Edit on the right hand side
5. Make sure "Download headers for subscribed folders" is selected