SUMMARY (of SUMMARY: sendmail (gethostbyaddr) warning

From: Andrew F. Mitchell (
Date: Fri Jul 26 1996 - 09:18:09 CDT

Well, well, well...the sun managers came thru yet again. Specifically
Michael Price Contractor <> who wins the bug prize
of, er,..well..."Thanks, Mike" ;-)

My problem was a

> > Jul 23 09:35:41 snipe sendmail[1669]: gethostbyaddr() failed

kinda deal. Pretty much everyone pointed the finger (correctly) at a DNS
config error on my part. The question was where?

Some suggested that I run nslookup (or dig) to check reverse lookups or MX
records on the hosts that were having problems. However, there were no
specific hosts (that I could find) that we were having problems sending
to - mail was coming in and going out just fine.
(too many responses to print all here, but that summarizes pretty well)

ANother suggestion was to run named with the -d flag and see if DNS coughed.
Not that I could see (but getting closer).
Thanks to

Casper suggested looking for a config'd interface as a problem.
Nope, not there, but getting *real* close now. ;-)
Thanks to Casper Dik <>

Finally, I got the suggestion to run sendmail in address test mode with the
flag -d0-8.20 -bt < /dev/null That did it. The first thing
that I saw was (names changed to protect the innocent (and stupid)):

snipe{root}3: /usr/lib/sendmail -d0-8.20 -bt < /dev/null
Version 5.x
canonical name: snipe
        a.k.a.: []
        a.k.a.: loghost
        a.k.a.: []
        a.k.a.: [yyy.yyy.yyy.yyy]

Well, is the name for yyy.yyy.yyy.yyy which is bound to
the virtual interface le0:nnn Uh, oh... Now that one was ok, but a second
virtual binding I had done was left without a reverse pointer in the DNS.
ouch. I had only checked 'ifconfig le0' after getting Casper's message.
I should have checked 'ifconfig le0:nnn' also. Oops.

So there was the problem. A virtual interface configured with an IP address
that had no reverse lookup. Even though no mail was attempted to that address
and no reference (by name or number) was made in the Live and
learn, eh?

Thanks to all the people that offered suggestions. If I have forgotten
someone, I apologize. All help was gratefully received. Thanks!


Andrew F. Mitchell, Network Systems Administrator,
The University of Florida Biotechnology Program, (352) 846-1733

"I don't like it, and I'm sorry I ever had anything to do with it."
                                                   - Erwin Schrodinger

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