On Mon, 6 Mar 2000, Nigel Metheringham wrote:
> Reading from the spec document....
> > Even if its address doesn't match `host_lookup', a sending host's real
> > name is looked up from its IP address if the argument it provides for
> > the HELO or EHLO command is the local host's own name, or the name of
> > one of its local domains, which seems to be a fairly common
> > misconfiguration.
>
> Does this extra logic actually gain anything, and would we be better
> dropping this special casing on DNS reverse lookups and just relying on
> the `host_lookup' config variable.
Well, I got fed up with hosts that don't follow the rules of RFC 821. I
run my hosts with lookups turned off (to save the DNS cost) but on these
hosts (cus.cam.ac.uk) I saw a lot of connections where the client said
HELO cus.cam.ac.uk
instead of
HELO the.name.of.the.client
Even worse are the ones that say
HELO 131.111.8.6
(i.e. *my* IP address). This makes the logs etc look very odd because
they are full of my host's name (or address) mixed up with other people's
addresses. [This might have been before the time Exim put HELO names in
parens.]
Clients that do that are in breach of RFC 821. In thinking what to do
about it, it seemed that a tidy thing would to to force a lookup in
order to get the correct name in the log. I decided that refusing such
HELO/EHLO commands would cause more trouble than it is worth.
Obviously, if people want it, the code could be thrown away or made
conditional.
--
Philip Hazel University of Cambridge Computing Service,
ph10@??? Cambridge, England. Phone: +44 1223 334714.
