On Sep 13, 13:05, Bill Bradford wrote:
> bash-2.03$ nslookup subatomix.com
> Server: localhost
> Address: 127.0.0.1
>
> Name: subatomix.com
> Address: 24.94.226.65
>
> bash-2.03$ nslookup 24.94.226.95
> Server: localhost
> Address: 127.0.0.1
>
> Name: okc-94-226-95.mmcable.com
> Address: 24.94.226.95
>
> DNS be brokie. I guess I"ll have to turn off the
reject-mailhosts-with-bad-dns
> requirement..
Um, not necessarily. You mis-typed the IP address on the second lookup.
subatomix.com is indeed a valid domain name, registered by Tierranet whose
nameserver (ns1.domaindiscover.com) will give you the A record and MX
record for subatomix (both point to 24.94.226.65).
However, there's no necessary correspondence between the domain name
registrar, DNS provider for forward lookups, and ISP who provides the
actual connection and address (usually also the DNS provider for reverse
lookups). The reverse lookup for 24.94.226.65 comes out as
okc-94-226-65.mmcable.com which isn't surprising. The reverse lookup is
done by the mmcable servers, since they own the address space. If you look
at Jeffrey's home page, it's URL is
http://home.mmcable.com/xoraxax/, so
that fits. Whether your mailserver will accept mail directly from
Jeffrey's machine probably depends on what his machine is calling itself in
the HELO and whether your mailserver does a reverse and forward lookup to
check (as you've implied).
If so, possible solutions are (1) turn off the double check, (2) have
Jeffrey's machine give its mmcable.com name when sending mail, (3) have
Jeffrey's machine relay mail through mmcable's server (assuming mmcable
really is his ISP), or (4) persuade mmcable (again, assuming they're his
ISP) to include his properly registered domain name in their DNS.
--
Pete Peter Turnbull
Network Manager
University of York
Received on Thu Sep 13 2001 - 14:56:22 BST