Outlook Email attachments behaviour

No sure this a norton issue but I have a client in a Mac environment. When they send me an email with a signature with just text it displays as expected in my Outlook 2007.  We both use pop accounts.  When they send an attachment the attachment is visible but signature fractures into 3 htm documents shouwn as attachments.  If they FWD an email same thing happens with sighnature but the FWD email also appears as a htm attachment.  Hasnt happened with any other clients.  Anyone have any ideas please?