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

>> [...blocking certain spammer domains...]

> 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)

How is the second one possible?  An MX record isn't capable of
containing anything *but* a FQDN.  (Or does this really mean "MX hosts
in nonexistent top-level domains"?)

As for the third one - do you actually mean "address record", or do you
specifically not want to talk to people with IPv6-only MX hosts?  Or do
you block only when *all* MX hosts are problematic?  (I have my MX
record split; my MX is dual-stack, but when I had a single MX host with
both addresses, I ran into trouble with a sender who tried IPv6, got
rejected for no rDNS, and didn't try the IPv4 address of the same MX
host, so I split it into two MX records, naming different names with
only v4 and only v6 addresses, even though both addresses actually
reach the same machine.)

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