We use imap and outlook for our customer service email box. We are constantly at war with it reindexing, damaging data files, and generally waiting on hour glasses. We have 10's of thousands of emails in various sub folders and would love if it would behave better.
Typically outlook likes to just hang and not give you any indication what the heck its doing. Thunderbird works a lot better but we are using outlook mostly for the calendar etc.