Exchange 2007 /exchange Not Redirecting

Exchange 2003 to 2007 migration. The new client access server role is put in place on a box with no other roles. A Exchange 2007 mailbox server exists on another server. Users who have an exchange 2007 mailbox on the 2007 mailbox server can login using https://mail.companydomain.com/owa. However when they use https://mail.companydomain.com/exchange they get the following error:

"You do not have permissions required to access this Web site. Please contact the Web site administrator."



However the username and password is right because if you go to https://mail.companydomain.com/owa it works fine.

https://mail.companydomain.com/exchange is meant to redirect them to https://mail.companydomain.com/owa automatically. To resolve this we installed 3 IIS components on the backend exchange 2007 mailbox server:
- ISAPI Extensions
- Basic Authentication
- Windows Authentication



After this /exchange redirected to /owa again as it should for 2007 mailbox users.