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Re: the "implicit-MX" rule and a proposed BCP

2004-02-16 03:25:08
On Fri, Feb 13, 2004 at 05:20:55PM -0500, Meng Weng Wong wrote:
Our MX server boggle recently got this error:

  when we tried to send mail to holborn-ed(_at_)real-life(_dot_)tm, the 
receiving
  host mailgate.real-life.tm[195.11.8.2] said: 550 Sorry, the domain
  "boggle.pobox.com" has no MX records. (in reply to RCPT TO command)

so mailgate.real-life.tm has an antispam rule that refuses all sender
domains with no MX records.  In a world where the implicit-MX rule was
deprecated, that behaviour would be the norm.

So what did we do?  We added MX records to all our mail servers.

I know the guy who runs the receiving mailserver in the above, and asked him
about it. His justification for requiring MX records is pragmatic:

----------------------------------------------------------------------------
boggle.pobox.com is a valid host, and not all hosts are required 
to have MX records.

This I know. By RFC it will try MX and then A (and if it finds and A that is
valid). But there are only rare occasions where it actually hits valid users 
(such as yourself) and I always keep an eye on what I reject too. Since I put
in the rule a good 30% of spam sent hits that spam rule, hence me using it.

It has an A record which is fine, and matching forward 
and reverse DNS too. 

Yeah, its more just people sending mails as 

xxx-wmw+P7Ey4RidKVwL9RKIPysbZW3QAKAYH7UyNDNZLOWtrDuTkK7Bz//0HpDZ/yRdT/Sf4BzaN0YAvxtiuMwx3w==
@public.gmane.org
(which scarely, as mention before, is quite sizeable percentage of my 
incoming spam!)
----------------------------------------------------------------------------

Regards,

Brian.


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