[166578] in North American Network Operators' Group
Re: Reverse DNS RFCs and Recommendations
daemon@ATHENA.MIT.EDU (John Levine)
Thu Oct 31 11:13:51 2013
Date: 31 Oct 2013 15:13:02 -0000
From: "John Levine" <johnl@iecc.com>
To: nanog@nanog.org
In-Reply-To: <20131031055204.GL3263@mail.incertum.net>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
>Mail admins wanting matching forward/reverse DNS and hostnames that
>don't "look dynamically generated" is probably more of a human than an
>RFC thing:
Right. Spam filtering depends on heuristics. Mail from hosts without
matching forward/reverse DNS is overwhelmingly bot spam, so checking
for it is a very effective heuristic.
Mail from hosts with names that look dynamic is also quite spammy, but
figuring out what looks dynamic is quite hard. I know someone who's been
tuning his regexes for years. For most people, third party lists like
the Spamhaus PBL are more reliable.
R's,
John
