[Kalmah]

I had the same problem once. A bunch of mail was getting 'returned' to me because 'a virus was detected on them'. I then ran a virus can and found that my whole computer was infected. Cleaned it out and then the returned emails stopped. I'm not sure how my account got effected by a virus on my system though because it was hotmail. I don't use any email programs. I suggest you scan for viruses.