Sendmail mailertable troubles

[Al Cooper]

I am attempting to use a Cobalt RaQ550 running MS/SA to "front" a series of
Exchange servers and provide spamming filtering.  I have MS/SA running with
no issues.  The RaQ550's sendmail.cf does not have support for mailertable
feature, so I edited the sendmail.cf file and added:

Kmailertable hash /etc/mail/mailertable

I then added a file at /etc/mail/mailertable in which contains the following
entry.

.mydomain.com        smtp:[172.16.0.76]

in which mydomain.com is the domain I want to forward and 172.16.0.76 is the
exchange server.

I pointed the MX records for mydomain.com to the Cobalt box.

I then restart sendmail and send a test e-mail to user at mydomain.com. I
receive the following error:

  ----- The following addresses had permanent fatal errors -----
<user at mydomain.com>

   ----- Transcript of session follows -----
554 5.0.0 MX list for mydomain.com. points back to (cobalt box)
554 5.3.5 Local configuration error

It looks like sendmail is not using the mailertable file to determine the
next hop for the mail.

What am I missing??????

Thanks for your help.

Al Cooper