Mail::SpamAssassin::Plugin::URIDNSBL(3pm) on Linux
The text 5f9e32bf47fb, as Debian 3.1 (Sarge) shipped it.
look up URLs against DNS blocklists This works by analysing message text and HTML for URLs, extracting the domain names from those, querying their NS records in DNS, resolving the hostnames used therein, and querying various DNS blocklists for those IP addresses. This is quite effective.