Second Exchange 2000 Server

I installed a second EX 2K server to join the exiting 1st EX 2K server, but not able to receive emails from 1st and outside while all outgoing mails are working properly. Could you please tell me what can resolve this problem?

– 1st EX 2K: mx 10
– 2nd EX 2K: mx 20
– one routing connector

Reporting-MTA: dns;testserver.test.com
Received-From-MTA: dns;web14203.mail.yahoo.com
Arrival-Date: Thu, 14 Nov 2002 09:50:09 -0800

Final-Recipient: rfc822;testuser@test.com
Action: failed
Status: 5.7.3
Diagnostic-Code: smtp;505 5.7.3 Must issue a STARTTLS command first
X-Display-Name: testuser

Thanks.