I'm working with Exchange 2000, in which, I am using the SMTP Virtual Server's "Deny Access" to block IP addresses which send spam, and to block countries who would have no other interest in what our company does. (example, why would people in China be interested in an apartment complex in Oklahoma, plus they could get to our web site, and call...)

Anyhow, my question is, if I want to block 202.0.0.0~203.0.0.0, with a subnet mask of 254.0.0.0 - do I need to use 202.0.0.0/7 or 203.0.0.0/7 ?

Thanks!