does anyone knows how to connect Exchange 2000 with Exchange 2003?

I mine that the one exchange (Exchange 2000 on windows 2000 server) stand for example in New York and
the second Exchange (Exchange 2003 on windows 2003 server) stand in L.A. .
The user in New york and LA should send local mail with help of this both exchange servers.

does anyone have a guide to do this thing?