Forwarding e-mail in Exchange Server 5.5

Our LAN of existing users is in the transition of moving and they would like their e-mails forwarded to their new locations while; 1)maintaining their old e-mail address and 2)forwarding their old e-mail address to their new e-mail account until allof their clients have updated their contact info. I keep hearing about the ‘Routing tab’. Where is this located?