[Mimedefang] OT: DNS sanity check

[Les Mikesell]

John Rudd wrote:
> Les Mikesell wrote:
> 
>> You can support a claim that it is a recommended best practice to
>> provide matching A and ptr records in your DNS.  It is beyond stretching
>> things to claim that refusing email is a best practice.
>>
> 
> You're like talking to a brick wall.

Yes, a brick wall won't pretend a requirement exists when it doesn't...

> Your counter-assertion against this behavior is completely unfounded.

I have no counter assertion.  Arbitrary choices are arbitrary.

> There is nothing that says you MUST NOT nor SHOULD NOT reject based upon
> the sender's bad DNS (the only prohibition that comes close is based
> upon the sender's bad HELO).  A sender who doesn't have matching A and
> PTR records is violating best practices.  It is perfectly reasonable to
> reject a sender's email when you know they're violating best practices.

It is perfectly arbitrary to reject on such a basis and there there is
no justification for the rejection in standards requirements.  You are
allowed to make arbitrary choices for your own site but don't claim that
it is because of a standards requirement.  I'm not sure I'd go as far as
calling it even a 'reasonable' interpretation of RFC standards in light
of 2821's "Sometimes a host is not known to the domain name system",
which points out that DNS recommendations are not strict requirements
for smtp.

-- 
  Les Mikesell
    lesmikesell at gmail.com