questionable email filtering policies?

Ken A. ka at
Fri Jul 24 16:18:31 UTC 2009

On 07/24/2009 06:39 AM, Florian Weimer wrote:
> * Chris Hills:
>> On the topic of mail rejection I have come across a few sites that
>> reject mail, even to [email protected], from domains that have one or more
>> ipv6-only MX records listed (i.e. a domain name with AAAA but no A
>> record(s)). The common factor seems to be mimedefang.
> Plain sendmail has got a similar issue, especially if the best MX is
> IPv6-only.  I learnt that the hard way---and it speaks for the quality
> of IPv6 testing that the "IPv6 considerations for SMTP" RFC (forgot
> its number) doesn't even come close to mentioning this issue,
> preferring to talk about bizarre reachability concerns. 8-P

Is it an antispam test that fails in sendmail, or does delivery fail 
after the first MX lookup is 'unexpected' (yikes)?

As a small ISP that runs our own mail for the most part, I'm curious if 
there are any lists out there of antispam tools that have been tested in 
a functional ipv6 environment.

By antispam tools, I mean things like mimedefang, snertsoft's milters, 
mailscanner, spamassassin (and dns perl modules), and other 3rd party 
milters or filters that might be less well known, but that do dns tests, 
or sanity tests of some kind (milter-dnsrbl, milter-regex, etc).


Ken Anderson

More information about the NANOG mailing list