Microsoft DNS on NT 4.0 SERVFAIL when no MX

[Michael St. Laurent]

I know this problem has been around for a while and was suposedly
fixed in Service Pack 4.  We have SP6a installed and are still
experiencing the problem and I'm at wits end.

We are using the split DNS model on our firewall.  The internal server
is an NT 4.0 system using the Microsoft DNS server.  When sendmail on
the firewall does its query to the internal DNS server for an outgoing
email, it gets forwarded back to the firewall.  The firewall does the
lookup and returns NOERROR and the SOA record as it is supposed to
when the MX record does not exist.  The Microsoft DNS server, however,
interprets this to mean that *it* should return SERVFAIL instead. 
This causes sendmail to defer the message with an eventual timeout
after five days.

Can someone tell me either how to fix the behaviour of the Microsoft
DNS server or configure sendmail to work around the problem?

Thanks