F[ On Wednesday, January 22, 2003 at 16:01:31 (+0000), Philip Hazel wrote: ]
> Subject: Re: [Exim] MX verification ACL
>
> On Wed, 22 Jan 2003, Drav Sloan wrote:
>
> > > on your dnslookup router. Of course, that will cut you off from quite a
> > > large number of Internet hosts.
> >
> > Blimey you think so?
>
> Oh yes. There are lots of one-box sites that don't seem to both with MX.
There are only about 17% of zones without an MX.
There are probably a lot more mail hosts without MXs.
http://www.menandmice.com/6000/61_recent_survey.html
> Personally, I wish the rules would change, because MTAs waste a lot of
> retries sending to bad domains that have A records but no MX. Often
> happens if a PC user mis-configures an MUA, for example.
Yes, quite a pain. I haven't allowed sender address domains without MXs
for quite some time on my own personal mailers, and I get few bounces,
but not using the A fallback rule for sending does get in the way.
On a related note:
Due to severaly interrelated security checks and changes in DNS resolver
replies Smail will usually no longer deliver to domains with invalid MXs
(i.e. it won't chase CNAMEs, and it never did allow bare IP addresses.
Only about 3% of known MXs are bad..... (and that survey matches my
mailer logs quite well too)
I would highly recommend that Exim not chase MX target CNAMEs any more
either, at least not by default.
--
Greg A. Woods
+1 416 218-0098; <g.a.woods@???>; <woods@???>
Planix, Inc. <woods@???>; VE3TCP; Secrets of the Weird <woods@???>
