DNS/SMTP/SmartHost problems

[Dave Wreski]

Hi all.  I've set up a split-dns between my internal DNS server and
external primary server in the DMZ, as described in the firewalls FAQ.

Now it appears that my primary name server can't resolve smtp.mydomain.com
when sending mail, despite the fact that using nslookup for both forward
and reverse works properly.

Using tcpdump on that interface while sending mail reports:

apps.2175 > smtp.mydomain.com.domain: 36971+ (38)
smtp.mydomain.com.domain > apps.2175: 36971 ServFail 0/0/0 (38)
apps.2181 > smtp.mydomain.com.domain: 29353+ (38)
smtp.mydomain.com.domain > apps.2181: 29353 ServFail 0/0/0 (38)
apps.2181 > smtp.mydomain.com.domain: 29354+ (58)

Then the mail sits in the internal mail server's queue with the following:

(Deferred: Name server: smtp.mydomain.com: host name looku)
                                   dave at nic.com

What could I be doing wrong?  In my zone files, I list smtp.mydomain.com
as the first MX host:

                IN      MX      10 smtp.mydomain.com.

Argh..  Not sure what to do next. Thanks for any ideas,
Dave