Sending Notes Developed attachment using Exchange Server

I have a problem related to Lotus notes development.The developement Group have developed an online request form using Lotus notes which will be automatically forward the mail to the next level for attention when send out using SMTP to internal recepients using Exchange Mail Server. The problem is my Exchange Server is in Singapore and having sites in US and Japan. The SMTP is set in the Server (Bridgehead) in the US. So, whenever we send out mail using SMTP..it always goes to the US before sending back to users eventhough the users are in Singapore Site. This is time consuming where it tooks long time to reach it's destination. How can I overcome this like if I want it to recognise if the reception is local then it use Singapore bridgehead to them instead of going all the way to US before returning. Anything can be done in configuration wise or progmatically which will relay the mail accordingly? How can the mail sent be recognised if they are internal or external and sent them out accordingly without having to go to US if the person is a local recepients.

Thank You.