TCPIP SMTP failed to send out our own domain email

I have installed one VMS (Itanium rx2800i2) server on our data centre.  The server came from US and I located in Canada.  The server SMTP running fine before it moved to Canada.   After the installation, I change the server SMTP alternate gateway to our site exchange server.  I can send out any global emails (such as .com,  ...) without issue.  When I send out email with our own domain, it failed.  My server domain is ourcompany.ca and alternate gateway is exchange.company.ca .  When I send out our domain email (such as desmond.or@ourcompany.ca) it loop on the SMTP queue but no any failure message.  The SMTP worked fine on US environment, and it has this issue after move to Canada.  

Does anybody know what cause the issue?  The exchange server and network administrators do not find any issue on their site.  

Thanks

Desmond Or