[Mimedefang] Is there a way to check body for specific text?

[Alton Yu]

Is there a way to check body for specific text like say if it had the 
text of a specific domain (viagra.com), to discard the message?

Someone used my email address as a envelope from address to spam and I 
keep getting bounced messages. I haven't figured out how to do this in 
mimedefang, but in postfix, I just use /etc/postfix/body_checks and have 
in the file something like:
/some text/	DISCARD SPAM

I would like to have a similar setup in Mimedefang.

Thanks!
Alton