Real World Questions, Real World Answers: MSOutlook.info
Some IMAP specific links:
Setting the Sent Items folder for IMAP accounts in Outlook 2013 or Outlook 2016
The Sent Items/Deleted Items folder is unavailable
Empty Inbox and other IMAP synching issues in Outlook 2013
IMAP performance in Outlook 2010
IMAP accounts and saving Sent Items on the server
IMAP and always download full items