Forward local email for nonexistent user to another server

[telescop]

Thanks for any help you can give me. I am trying to get sendmail to deliver local mail for nonexistent users to another server. Example: ServerA has user1domain1 and he is trying to email user2domian1 which resides on ServerB. Currently, I get "unknown user" error. Is there a way to tell sendmail "If you have local mail for domain1 but the user does not exist forward the message to ServerB. Hopefully this is not too confusing. Just looking to test another mail server with some users but still get local mail between them.

Thanks again.

[aram535]

Your distro may already come with a /etc/mail/virtusertable, if so just upgrade, make, restart sendmail.

If not, in sendmail.cf:
-> Kvirtuser hash -o /etc/mail/virtusertable.db

create a /etc/mail/virtusertable containing:
-> @foo.com foo@somewhereelse.com

-> use makemap hash to createthe .db file