Re: [anti-spam-wg] Domains with MX set to localhost

  • From: Jay Daley jay@localhost
  • Date: Wed, 11 Jan 2006 14:24:14 +0000

> We block a domain if:
> 
> . the MX host is "." (following draft-delany-nullmx)
> . the MX host isn't a FQDN
> . the MX host has no associated A record at all
> . the A record of the MX record is localhost, RFC1918, link-local, class
>   D/E, or a limited set of bogons (yes, I'm watching IANA allocations)
> 
> And we do this test for all primary MX hosts, except that in some cases
> we also look at lower priority MXes, in case the primary MX points to
> private IP space for example (which would be bad, but it would "mostly
> work").

Is there any legitimate reason that anyone knows of for people to set 
their MX records like this?  If not then it seems too easy for a registry 
to scan the zones of all the names it knows about to look for these 
telltale indicators and compile a list of spam domains.

Jay Daley
Director of IT
Nominet UK