Name or service unknown - postfix

[php4u at pacbell.net]

While running Centos4 (RHEL4) with Postfix and Bind9, I am recently
seeing an error message - mail being bounced. I have never seen the
error message before, and not sure if it's a Postfix or Bind message. I
have exhausted all of my sources, and need to post my problem here.
Perhaps the answer will help someone else too.

_____________

mail header showing error;

			The Postfix program

<shawna at domain.com>: [mail.domain.com]: Name or service not known

<suzanne at domain.com>: [mail.domain.com]: Name or service not known
Reporting-MTA: dns; mail.domain.net
X-Postfix-Queue-ID: E28FD664BAE
X-Postfix-Sender: rfc822; rbrown at domain.net
Arrival-Date: Wed, 20 Jul 2005 05:34:41 -0700 (PDT)

Final-Recipient: rfc822; shawna at domain.com
Action: failed
Status: 5.0.0
Diagnostic-Code: X-Postfix; [mail.domain.com]: Name or service not
known
----------------------------------

Bind shows no errors when performing RNDC reload, and the mail error
shows up in the mail log.

Suggestions?

thanks in advance 
Ralph