[exim] Multiple domain Hosting

Hi all ,

I know how to setup exim for Multiple domains . In the domainlist
local_domain= domain1:domain2

I'm already hosting mail for domain1 and ready to start hosting mail for
domain2 . In domain2 only 1 person should be receiving emails from that
2nd domain. Is there a router that says any e-mails from domain2 forward
to user@???. I hope this make sense .

Thank you all in advance.
-Jeremy