[plug] tricksy email and strange attachments

[sol]

Hi there,

I am the administrator of a mailing list (GNU Mailman on a Debian Woody 
server) with about 700 people on it. An hour ago it received a posting 
"allegedly" from on of the handful of people that are allowed to post to this 
list (it's a highly regulated news announcement list). But the subject was 
"Sexy Japanese Girls Photos" or something like that and it came with a file 
"press.scr".
Two problems:
1) I checked with the approved poster, and he hadn't sent any email, let alone 
strange attachments. I think that someone is "faking" the email address 
headers. Is this possible? How can it be blocked?
2) Has anyone come across "press.scr"? I suspect it's a 'doze virus and that 
half of my email list is about to get it. NOT HAPPY BILL!

cheers,
sol