A significant part of the population HAS friends overseas, so you cannot block based on Country.
Also remember that the e-mail actually originates in the US, it just takes a detour through an open relay.
There are services that keep track of known open relays, e.g. Maps
and allow your mail server to reject all connections from open relays, dial-up IPs, etc. anything that circumvents legitimate SMTP servers. This needs to be done at the ISP.
My ISP just transitioned to attbi, and a new feature that is enabled by default(!) is a service by Brightmail
. It basically utilizes a network of strategically placed fake e-mail accounts, that, when hit, will generate appropriate filters that are immediately deployed to the mail-walls at all subscribing ISPs.
During the last week, It trapped about 15 genuine spams (they are placed in a special online folder for inspection, but get automatically deleted after some time). It only missed 2 SPAM e-mails. This is actually not bad!
Still, all my SPAM gets reported to spamcop
.[text was edited by author 2002-02-17 05:39:20]