Problem with Two Exchange Servers Communicating With One Another from Separate Networks

Hello,

I have two Exchange 2003 servers, one master and one member.  They're on separate networks.

For example, ex01 is in 192.168.1.0/24 and ex02 is in 192.168.2.0/24.  If I was a machine in 192.168.1.0/24, I would be able to communicate to the port 25 of ex01 with no problems:

220 ex01 Microsoft ESMTP MAIL Service at ....

For some reason, when I try to communicate on the SMTP port 25 from 192.168.2.0/24 going to ex01, I get:

220 *******************************

And any input results in Unrecognized command.

I suspect it has to do with relaying but for testing purposes I've set the SMTP to 'Allow all except below' with the list being empty on both servers.  And yet I still get the same error.

How can I isolate the issue?

Thanks.

Neil