This option is disabled by default. You can let Gnus consult the
blackhole-type distributed spam processing systems (DCC, for instance)
when you set this option. The variable spam-blackhole-servers
holds the list of blackhole servers Gnus will consult. The current
list is fairly comprehensive, but make sure to let us know if it
contains outdated servers.
The blackhole check uses the dig.el package, but you can tell
spam.el to use dns.el instead for better performance if
you set spam-use-dig to nil. It is not recommended at
this time to set spam-use-dig to nil despite the
possible performance improvements, because some users may be unable to
use it, but you can try it and see if it works for you.
The list of servers to consult for blackhole checks.
A regular expression for IPs that should not be checked against the
blackhole server list. When set to nil, it has no effect.
Use the dig.el package instead of the dns.el package.
The default setting of t is recommended.
Blackhole checks are done only on incoming mail. There is no spam or ham processor for blackholes.