DNSBL – Country Lists

These are a large number of lists maintained at http://countries.nerd.dk/ which identify whether a given IP address is in a particular country.

In their own words …

The zone contains information which can be used to determine whether a given IP address resides in a given country, thus making it possible for the users to filter out mail from a specific country using standard methods. For example my own mailserver is configured to reject mail from hosts listed in cn.countries.nerd.dk, which means that I should reject most mail sent from or through a mail-server located in China.

The specifics of identifying when a given user is actually in a given country can be a little difficult. It is not entirely uncommon for large corporates to arrange that all of their internal traffic from around the world routes out of a single gateway in a single country.

Even given the above caveat judicial use of country blocklists can dramatically reduce spam.

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