[RFCI-Discuss] about FQDN for our smtp servers (was RFCI-Discuss Digest, Vol 39, Issue 4)

[Alex van den Bogaerdt]

On Thu, Apr 13, 2006 at 09:27:39AM -0700, Administrative Account wrote:

> 	I'm claiming much worse than that;  In the face of the contradictions
> in RFC2821 and other RFCs, the only clear requirement is that the HELO argument
> must resolve (to anything whatsoever).  And given the MUST requirement that
> mail can not refused to the basis of a non-match between the argument and the
> client, the argument needn't even be related to the client.  For the worst
> possible case one could even use the root as an argument and meet all of the
> stated requirements.

2821, which isn't a standard, section 4.1.1.1 means: if the host has a
host name available (and most have!) this host name must be used.  Only
when such a name is not easely available, this rule does not apply.

_Its_ host name.  Not _a_ host name.  Not any random valid domain.

> 	There are two different things here - the likely intent of the RFCs
> and the actual wording;  Your statement is unsupported and you do not offer
> any argument to back it up.

Excuse me.  We were not talking about what is happening in the wild.
We were discussing the RFCs.

Yes, people drive too fast.  That does not make it legal, and you cannot
get away with it by saying "but everybody does it".


You got lost in your own arguments.  You have proven that a MX record
is a FQDN.  I don't have a problem with that.  But this does not make
it a valid EHLO parameter.


You:
> Now regarding RFC1123 section 5.2.5, again there is no requirement
> here (despite that in RFC2821) to resolve to an 'A' RR

rfc1123, section 5.2.5:
> The sender-SMTP MUST ensure that the <domain> parameter in a
> HELO command is a valid principal host domain name for the
> client host.

A valid principal _host_ domain name.  Not a random valid domain name.
_For_the_client_host. Not just any host domain name.  Not my host name,
not an MX record, etc.