I am getting a lot of spam on my accounts from over seas IP addresses. I have been researching some ways to block all non USA IP's and have found the following;
GEO IP
.htaccess
/etc/host.deny

The problem I am having is that non of these actually block incoming IPs via email (unless of course I have just not found the right article yet that explains it the right way).

I am looking for a way to block all non US IPs from sending emails, any suggestions?