Georges,

  Are you reading your own messages when they come back through the list?  At the bottom of every message is a advert. for "FREE Easter emoticons", with a link to:

www.incredimail.com/index.asp?d=54475

It's not appearing on anyone else's messages.  It pretty much has to be getting appended by either your mail reader or by your mail provider.

That's why I suggested earlier that you look into an independent mail service.