Outlook frequently hangs when fetching new IMAP headers in larger folders
(>250 messages). It fetches the first batch of headers, then when it gets to
message number 249, it says it's flushing change to the local cache and
hangs there forever (or at least all night). Once this happens, every time I
try do access the folder it hangs at message number 249 again.
I've usually been able to clear up the problem by deleting the .pst file
which contains the header cache and reloading the folder, but even this
doesn't always work.