Exchange forwarding (external)

I would create an OU for all external recipients.
Within the OU
1)Create a contact
2)Assign an SMTP address.NB This is the Forwarding smtp address of the user.
3)Open ADUC
4)Navigate to user whose mail to forward/Properties/exchange general/delivery options,There you have forwarding address/modify to the external recipient you want to forward.If you wish your exchange to hold copies of mail check the box to deliver to both mailbox and external address
5)You are done