We are looking for a way to be able to block spam based on geographic location by filtering using geoip.

context: we rarely have any email correspondence outside of the USA, so we would like to block all incoming email outside the US except for maybe one or two countries.

After a little Googling I have found a couple of solutions that may work (or not), but I would like to know what other sysadmins are currently doing or what they would recommend as a solution.

Here is what I have found so far:

Using PowerDNS and its GeoIP backend it is possible to use geoip for filtering. Normally this backend is used to help distribute load as a kind of load balancing but I dont see why it couldnt be used to kill spam as well?

Possibly use the Maxmind lite country database and some scripting to do a similar job.

Ideally what I am looking for is a solution that would handle decent load and scale well too...aren't we all! ;)

Thanks in advance for your help! :-)