strange sendmail problems

[Thierry Lacoste]

Hello,

I experienced a strange problem with sendmail on FreeBSD 6.1
which happened during a routing problem on a network which
isolated my network from the outside.

On five out of seven boxes my logs started to show (capital names
used to hide real ones) :

Aug 30 15:53:13 MYHOST sm-mta[6247]: l7UAqbOp091438: to=USER at MYDOMAIN, 
delay=03:00:00, xdelay=00:00:00, mailer=esmtp, pri=618410, 
relay=MYMAILER.MYDOMAIN., dsn=4.0.0, stat=Deferred: Name server: 
MYMAILER.MYDOMAIN.: host name lookup failure

Running an MX query with nslookup on MYHOST was correctly giving
MYDOMAIN   mail exchanger = 1 MYMAILER.MYDOMAIN.
and 'host MYMAILER.MYDOMAIN' was correctly resolving the name.

The problem did not show up on two boxes.

All boxes run 6.1 and have default sendmail configurations.
The only difference that I can see is that the two unaffected boxes
run dhclient while the affected ones have static IP but I don't how
it could affect the issue.

Any idea what could explain this?

Regards,
Thierry.