I am having the same problem. It started when I moved some old messages from
a system upgrade folder into my in-box. I could delete a few manually, but
now it's stopped deleting anything, and comes back with an 'unknown error'.
"Cheryl of Exeter, NH" wrote:
> Keep getting 'Unknown error has occurred' when try to delete messages out of
> deleted box. I already deleted the mail that I could delete individually. Now
> I'm left with a bunch of deleted mail that can't be permanently deleted. HELP!