Can i deduce from this that you have blocked PSI
We did. Cut the spam attempts here by about 75%, and I haven't had any
complaints from customers. We subsequently switched over to Sendmail 8.8.6
with filtering, of course, but I don't think we've bothered to remove the
PSI filter from our router... 
Bad attitude, I know, and now I'll probably have to go remove it, so I can
feel like I'm still one of hte good guys, promoting connectivity and trust, etc.
-Bill