check message body/subject for spam?

[Don Ireland]

Hi everyone.

I have a contact form that allows visitors to send messages to me.  Some 
nimnod is using it to send me ads wanting me to use his "Search Engine 
Optimization" service.

Because the form sends messages as though it is ME, the mail server 
doesn't check messages received from my form through SA.  I'm a user on 
a shared hosting service so I can't change that.

If I write the message/subject to a file (so that it looks like a 
message without most of the headers), can I run it through SA and make 
sure that it's not spam?

TIA!

Don Ireland