Using different Mail Servers

Is there a way to make the AS/400 route SMTP e-mail to different servers
based on where it's going?  For example if this is internal e-mail and it
all goes to xxx@xxxxxxxxxxxxxxxx it would send it to a local IP address but
if its xxx@xxxxxxxxx it would go to our main exchange server?  The idea is
that we would cut down on e-mail traffic over the internet and help
performance on the exchange server.   Also we are looking at some fax
software that you can send as an e-mail and it will convert to a fax.  So we
do not want these fax e-mails to be sent over the internet and they should
stay at our local IP address.

I don't know if there is a way to setup rules or not.  

Thanks