[Mimedefang] Mimedefang 2.43 bouncing messages with wrong unkown user

[Wayne]

Sorry for the simple question but I am bouncing messages back to one
particular server saying the account is unknown but this is not the user the
messages was sent to. The server seems to be a Postfix server. I haven't
seen this happen to any other server but I can't be sure. I use Sendmail
8.12.11 and mimedefang 2.43 to filter messages and relay them to my
Communigate server. I have it setup using md_check_against_smtp_server. This
is the rejection the user gets.

 The Postfix program

 <someuser at hamilton.net>: host smtp1.hamilton.net[208.6.238.14] said: 554
5.7.1
    adifferentuser at hamilton.net unknown user account (in reply to RCPT TO
command)

How can I handle this correctly ? I guess I'm not sure how this is
happening.

Thanks
Wayne