I'm writing here because couldn't find a newsgroup for Windows Mail.

On a friend's computer with Windows Vista and Windows Mail, an e-mail is
stuck in the Outbox and it can't be deleted. When you try to move or delete
it, there is an error message. The message has been stuck there in the
Outbox for several days.

I turned off Windows Mail, found the folder that contains the e-mail and
deleted the Outbox, then restarted Windows Mail in order for the Outbook to
rebuild itself. It still had the message in it.

Any ideas?