New Exchange Server - The recipient name is not recognized

[draqstar]

After Installing Exchange 2000 and setting up a few users I get the Following Error.
"The recipient name is not recognized"

I can Send But Not Receive. I use Routing to the Server A which is eg Acme.com

My Remote Server acme123.com Sends to Recipeinets on Server A, And they Receive the Email but Can not Reply:

The Following Erro Message Comes Back.
did not reach the following recipient(s):

'Jack Frost' on Tue, 30 Jul 2002 16:42:18 +1000
The recipient name is not recognized
The MTS-ID of the original message is: c=au;a= ;p=Acme group
limi;l=CEMPENNT010207300642P8LBN215
MSEXCH:IMS:Acme Group Limited:CEMPEN:CEMPENNT01 0 (000C05A6) Unknown
Recipient

Any Clues Here.