I gather you're working with a large number of emails. Right? Otherwise, i.e. for personal emails or a small number of emails, I don't think this would be a very significant problem; you could just solve the issue for any instance where you discovered an invalid email address and the problem would be very limited in scope. So, again, you seem to be working with a large number of emails. In your original post, you said, "I get 100's of outlook attachments in an email from my vendors." So, you have 100's of vendors for which you do not have a valid email address?