Re: 7. BCP - Mail Administrators: Checking HELO (was: [Asrg] 0. General - Administrative - for M. Wild)

[waltdnes@waltdnes.org]

On Sun, Aug 31, 2003 at 02:09:34AM +0200, Brad Knowles wrote

> 	If it's behind a NAT, how would it know the external DNS name? 
> If that IP address on the NAT device is dynamically assigned and the 
> machine is not an intelligent host running software capable of 
> updating a dynamic DNS record (as 99.999% of all NAT/router devices 
> are almost certainly going to be), then how would the internal host 
> know what this external DNS name is?

  That point is moot... because if you're sending direct to the remote
MX from a dynamic IP address, there'll be a helluva lot more machines
rejecting you for being on a dynamic address than those worrying about
a syntactically correct HELO.  IOW, your mail is a lot more likely to
be accepted with an incorrect HELO from a static IP address.

> > One could argue that if they don't understand DNS, they shouldn't
> > run a mail server.
> 
> 	I would like to be able to make such an argument.  I really 
> would.  Indeed, I could even see making such an argument part of a 
> BCP, but only if the recommended practice did *NOT* involve rejecting 
> the connection outright just because they did not have reverse DNS 
> properly configured.

  How about total lack of rDNS ?  I block on that, not on mismatching
rDNS.

-- 
Walter Dnes <waltdnes@waltdnes.org>
Email users are divided into two classes;
1) Those who have effective spam-blocking
2) Those who wish they did

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