[CLUE-Tech] Sendmail on a local network

[Jed S. Baer]

On Tue, 15 Jul 2003 11:17:39 -0600 (MDT)
Jim Ockers <ockers at ockers.net> wrote:

> > Q1: Why doesn't sendmail like an IP address in the destination and
> > prefer a hostname instead?
> 
> Sendmail is quite tightly integrated with the DNS.  It uses many
> functions of DNS for proper reliable mail delivery, which is why a DNS
> name is best for the address.

Sendmail (or, I'm told, any SMTP MTA) wants to look up the MX record so it
knows what the designated mailserver is for a host/domain. Since it would
be legal to have a completely numeric host/domain name (even though there
aren't any numeric TLDs allocated), the MTA doesn't distinguish an IP
address as such. I discovered this once, when I wanted to send e-mail to a
postmaster to tell him that his DNS was busted. I somehow discovered the
IP address of the right machine, but kept getting bounces.

Anyway, I discovered a way around it, although I seem to have deleted the
e-mail I thought I'd saved, which showed how. I think it was to enclose
the IP address inside brackets, e.g. [192.168.22.5]. You might have to
google a bit to find out the exact syntax.

jed
-- 
... it is poor civic hygiene to install technologies that could someday
facilitate a police state. -- Bruce Schneier