[ On Thursday, October 23, 2003 at 11:59:26 (+0100), Tony Finch wrote: ]
> Subject: Re: [Exim] Refuse connection if no MX for sending host
>
> So in most cases there's no direct relationship between the machine's
> hostname and relevant MXs -- this is even more evident in the Demon
> case where the customer domains are in demon.co.uk but the machine
> names are in mail.demon.net. Note also that it would be wrong to have
> an MX for plum.csi.cam.ac.uk since there are no valid email addresses
> @plum.csi.cam.ac.uk.
That's wrong. There is always at least one valid mailbox address at
every mail server that answers and speaks SMTP on port 25 (and it _must_
be valid for both the host name of the mailer as well as for a domain
expressed as a literal IP address).
There _should_ always be an MX for every domain name that is a host name
of a mailer, and the target name of the MX should be the same domain
name:
mail.weird.com. IN A 204.92.254.2
IN MX 1 mail.weird.com.
Anyone too lazy or ignorant to configure the DNS for their mailers in
this way is doing a disservice to the Internet community.
That said I will note that even on my home system I don't check for an
MX for the sending client host. Checking that the helo name resolves to
the client's source address is sufficient.
--
Greg A. Woods
+1 416 218-0098 VE3TCP RoboHack <woods@???>
Planix, Inc. <woods@???> Secrets of the Weird <woods@???>
