Drifting OT (was Re: FW: "no data known" vrs "host not found")

[James Griffin]

Kevin Darcy wrote:
> 
> Will Yardley wrote:
> 
> > In article <a8ch5j$afb at pub3.rc.vix.com>, Barry Margolin wrote:
> >
> > > Sendmail has traditionally done an ANY query so that it can get look up the
> > > MX and A records in one query, rather than first doing an MX query and then
> > > an A query if that fails.
> > >
> > > I'm not sure if this is a configurable option or it has changed in recent
> > > versions.
> >
> > i could well be wrong, but i think this changed as of 8.10 or 8.11.
> 
> I believe sendmail uses ANY queries up through 8.11.
> 

Correct.  Just ran a test and checked the query log with
sendmail-8.11.6-3.

$ /usr/sbin/sendmail webmaster at www.gsa.gov < /dev/null

Produces the following:

Apr 03 07:54:43.723 client 127.0.0.1#1207: query: www.gsa.gov IN ANY
Apr 03 07:54:43.803 client 127.0.0.1#1207: query: www.wip.gsa.gov IN ANY
Apr 03 07:54:44.026 client 127.0.0.1#1207: query: www.wip.gsa.gov IN MX
Apr 03 07:54:44.078 client 127.0.0.1#1207: query: www.wip.gsa.gov IN ANY
Apr 03 07:54:44.178 client 127.0.0.1#1207: query: www.wip.gsa.gov IN A

Interesting that it took five queries!  Have to look into that, I guess.

I also found an interesting DNS/sendmail interaction that I had not
expected.

On my test lan, I have a machine corinth.athena.inc. that sometimes runs
an http/s server but not mail servers.  In the athena.inc. zone were:
   athena.inc. CNAME corinth.athena.inc.
   athena.inc. MX 5 sparta.athena.inc.
   along with the usual A RRs.

sendmail on sparta was configured to accept mail, but only for the FQDN
sparta.athena.inc. and localhost.  It was not configured to accept mail
for the domain athena.inc.  As a result, mail to <mailbox>@athena.inc
would bounce (after 3 days) as undeliverable - athena.inc. Not
Responding.  Which of course was true since there is no MTA running on
corinth.athena.inc.  

The solution is to add a "sendmail alias" for athena.inc. to the
appropriate sendmail configuration file ('access' in this case).  Now
sendmail would accept the MX RR as a source for information rather than
ignoring it and using the chain of athena.inc. ->CNAME
->corinth.athena.inc. ->A ->192.168.1.3 -.No MTA connection refused.

FWIW