Try this Microsoft fix:
http://support.microsoft.com/default.aspx/kb/941090
"Messages may be stuck in the Outbox when you use Windows Mail on a
computer that is running Windows Vista"
That page offers two download options. Unless you know for sure
you have 64-bit Vista, use the 32-bit option.
Although only 'Outbox' is mentioned, it will enable removal of stuck
emails from any folder.
--
Gary VanderMolen [MS-MVP WLM]
"dbayels" <> wrote in message news:2E09A966-C8F6-4543-95BD-...
> can you please help me with deleting a message in my inbox, "An unknown error
> has occured" appears