[ On Monday, March 29, 1999 at 20:08:33 (-0000), Pollywog wrote: ]
> Subject: RE: [EXIM] Bug#35221: Another anti-spam idea
>
> On 29-Mar-99 Mark Baker wrote:
> > On Mon, Mar 29, 1999 at 10:40:26AM -0500, Brian White wrote:
> >>
> >> It would seem that "pobox.com", as part of their anti-spam filter, will
> >> refuse mail coming from addresses that don't have an MX record (or maybe
> >> no MX _or_ DNS entry, I'm not sure).
> >
> > You shouldn't refuse mail based on absense of a DNS entry, as that could be
> > due to a problem with the DNS.
> >
> Very true. I had to add two more DNS servers to my record at InterNIC because
> every so often, my mail to AOL addresses would bounce because they did not
> find a DNS entry for my domain. A few minutes later, my mail would go through.
Wait a minute here Mark et al. That's a load of rubbish. If the DNS
doesn't work then SMTP won't work either (at least not on the public
Internet). You *MUST* have a valid MX (or A) RR in the DNS in order for
an MTA to find your host and connect to the SMTP port. If the sender's
address isn't equally well supported in the DNS then they're not going
to be able to receive a bounce (and maybe not even a reply) from your
MTA (or you) either. (Well, yes, it's possible to use literal IP
addresses (eg. "[192.168.1.1]"), but those are obviously not very
user-friendly, prone to change, and only really for use in emergencies).
If not having DNS is a frequent problem then you've probably got a
configuration error in your DNS, just as you discovered. There's a very
good reason why you want your domain's primary DNS servers to be very
reliable and on well connected, but totally un-related (routing wise)
networks. At the very worst you want your domain secondaried by your
upstream provider, but ideally you'll want someone on the other side of
the planet to officially secondary it too.
On the other hand if you really do want to accept e-mail from every IP
address on the planet, regardless of whether or not you'll be able to
send bounces back to them, or even to reply, then be my guest, but don't
be telling folks that they have to do likewise.
--
Greg A. Woods
+1 416 218-0098 VE3TCP <gwoods@???> <robohack!woods>
Planix, Inc. <woods@???>; Secrets of the Weird <woods@???>
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