503 Polite people say HELO first

I’m running Exchange 5.5 with SP3. I can send to every address except one. That server will except mail from everyone except me.

SMTP LOG:
05/22/2000 11:36:13 AM : A connection to 208.198.163.2 was established.
05/22/2000 11:36:13 AM : <<< 220firewall SMTPXD version 57 ready at Mon, 22 May 2000 Central Daylight Time 05/22/2000 11:36:13 AM : >>> EHLO mail_server.leeperderose.com

05/22/2000 11:36:14 AM : <<< 200 OK 05/22/2000 11:36:14 AM : >>> MAIL FROM:
05/22/2000 11:36:14 AM : <<< 503 please introduce yourself, first 05/22/2000 11:36:14 AM : >>> QUIT

05/22/2000 11:36:14 AM : <<< 221 firewall closing connection I also have 2 domain names on 1 IP address, both using the same Exchange Server.