I've got an Exchange 2003 environment coexisting with Exchange 2010 newly deployed.now i have a single exchange 2003 handling mailboxes and user access along with 2 exchange 2010 deployed with DAG technology both holding CAS/HUB/Mailbox roles. i decided to keep using EX2003 as internet-facing user access as it is redirecting 2003 & 2010 mailbox users to their respective servers quite fine. only having issue once we try to access OWA from internet..OWA service running on ex2003 redirect clients to the 2010 server's internal name.for example if we use ex2010s1.mycompany.local for internal name and mail10.mycompany.com for external Dns name, still exchange 2003 refers clients to ex2010s1.mycompany.local while they are accessing from internet since I've changed the the Internal and External URLs into mail10.mycompany.com on exchange 2010 but still clients will be redirected to ex2010s1.mycompany.local while connecting to 2003 OWA ! Some more changes should be made to solve the issue??