I had this working in the past. Our server crashed and had to be rebuilt.
I had alternate email accounts for my users through Exchange using a different domain name- built into SBS2003
Example (made up domain name):
My current business domain: ABCDEFGHIJKL.COM
I changed the MX/a records to point to my exchange server with the registra I purchased the domain from.
The owner realized that it's hard to communicate the above domain name for his companies emails - Joeexample@ABCDEFGHIJKL.COM to his clients.
He purchases another domain name: ABC.COM from a different registra.
I connected to that registra an pointed the MX/a records to my server@ABCDEFGHIJKL.COM and our static IP
I went into the Server manager within SBS 2003
I opened a the user properties and choose the E-Mail Addresses tab
I created a new SMTP account using the newly purchased domain name
I get this message when I attempt to send an email:
Your message cannot be delivered to the following recipients:
Recipient address: Chris@ABC.com
Reason: Remote SMTP server has rejected address
Diagnostic code: smtp;550 5.7.1 Unable to relay for Chris@ABC.com
Remote system: dns;server@ABCDEFGHIJKL.COM (TCP|xxx.xxx.x.xxx|40174|xx.xx.xx.xxx|25)
What am I doing wrong? What did I forget to do?