cannot forward a contact from Outlook

[Charlie]

Hi,
I have a problem with Mailscanner (and so does one of my clients).
Whenever I try to forward a contact in Outlook 2003 through my SMTP server 
with Mailscanner turned on, the recipient instead receives a file called
'Untitled Attachment.dat'.

This is the way that I am forwarding a contact:
Contacts
Open specific contact
Actions
Forward

This method works when I use another SMTP server that doesn't have 
Mailscanner turned on.

Please can someone help me on this?
Thanks