I need to know if there is a simpler, and more extendable way of configuring my mail domain.

Currently I have a linux server running sendmail which is running as a testing infrastructure for product development. This machine forwards emails to a PC running a java application that based on the address re-routes the messages to further SMTP servers (exhange, domino etc) at the user access points.

So basically it looks as follows where A is the linux box, B is the PC running the java app and C1 through C4 are the SMTP servers ...

All the java app is doing is looking at the address in the form:
and then based on what domainCx is routes to the server responsible for processing mail on the Cx domain.

Can I do this with sendmail so I can get one less mail hop without having to go and redo all the user configurations and addresses as this wall also impact a whole PKI system which is just not feasible.

Any help with this would be greatly appreciated ... oh I best mention I am NOT a sendmail guru.

Oh I forgot to mention the java app doesn't generate error emails if it cannot route a messages, so badly addressed messages have a tendancy to just dissappear ... hence I want to make the java app ... dissappear and taste its own medicine!