[ On Thursday, October 21, 2004 at 18:25:28 (+0300), Stuart Gall wrote: ]
> Subject: Re: [exim] hostname and HELO/EHLO response
>
>
> It might be worth mentioning What RFC ?
RFC 1123 5.2.5
(note that the pending new RFC for SMTP, 2821, says very much the same,
using approximately the same confusing and misleading wording, though of
course RFC 1123 still prevails as the overall host requirements RFC)
> Last RFC I read on SMTP said you are not supposed to reject on helo
> what ever it contains.
Then you did not quite read it 100% correctly. RFCs cannot dictate site
policies.
What that section in the RFC does say is that a client "MUST" greet a
server with its true and verifiable canonical hostname.
(of course that RFC is self-contradictory and thus very misleading to
those who do not first learn what RFCs can and cannot do)
Nobody is forced to do that either -- and many sites will allow SMTP
clients to lie about their hostname, or to use otherwise bogus or
invalid hostnames.
However the whole point is that if a sending site wants to maximize its
ability to deliver mail to arbitrary third party domains then it "MUST"
use its proper, verifiable, canonical, hostname. It's just like going
to a meeting and lying about your name when you introduce yourself to
anyone -- the result is not always going to be what you might hope for.
(yes the IP address literal trick works most places too, but not
everywhere)
--
Greg A. Woods
+1 416 218-0098 VE3TCP RoboHack <woods@???>
Planix, Inc. <woods@???> Secrets of the Weird <woods@???>
