Outlook meeting invite error reports.

Ive got an issue with a certain user, If this person is ever sent a meeting invite they will receive the invite but the person who sent it will get an error report stating:
“The following recipient(s) cannot be reached: .All another test on 17/03/2009 15:19 . Check the e-mail address, or contact the recipient directly to find out the correct address.”

.all another test is not one of our current ditribution groups. The users account has no forwarding setup.

Has anyone got an idea what this
could be?

Exchange server 03