Ondine wrote:

Another detail - if I wait long enough, Outlook will eventually manage
to sync the folders and my messages will reappear - but all the unread
items will be duplicated, the duplicate item will initially have a
size of 0kb, no attachments will be listed and my email address will
be in the 'To' field about 12 times! A short while later the folders
sync again and these duplicates disappear (but not before they have
all been copied by my Rule to another folder unfortunately). I reset
the Current View for my Inbox but it hasn't helped.

Naturally messages you read will "disappear" from the Unread Mail folder.
However, they shouldn't vanish from the Inbox unless they're marked for
deletion. Are you subscribed to the IMAP folders? Do you download the
entire message and not just the headers?

Franky, I find Outlook's IMAP transport to be less than robust.
--
Brian Tillman [MVP-Outlook]