Unauthorised mass mailing in Outlook

[Waterlow]

Can anyone help please?.
Every time I download my e-mails, I get many failed delivery messages to
addresses that I have not (knowingly) sent e-mails to. The titles of these
e-mails suggest that the original messages were spam. There is no sign of
these messages in my sent items folder.
I have updated my virus scanner (McAfee) and run a full virus scan several
times, and there no viruses reported. Any ideas because I would hate to
think I am unwittingly propogating spam, and my inbox is overflowing.

 

[DL]

Generally these returned mail msgs are another form of spam, allthough it
could also be that someone who has your mail address in their address book
has an infected PC.
Simply delete them