AVAST 5.0.462 outlook mails not acanned ,error message

avast 5.0.462 is not ablt to scan the messages i receive as well as what i am sending. the following error message pops up every time and i click on ok to send a mail.
even the version 4 of avast also gave me the same problem.
anyone have the same problem?
and anyone can help me or suggest a solution for the same to me?

help in this regard is appreciated!.