Exchange 2010 CAS and Exchange 2003 OWA server are co-existing. I've already specified the exchange2003URL parameter for the redirection in the exchange command shell. For exchange 2003 mailbox users, I can successfully login directly https://ex2k3server.domain.com/exchange.
But If I login via https://ex2010.domain.com/exchange, I get redirected (exchange 2003 login prompt) then
when I enter the username\pwd, I get 500 Internal error at https://ex2k3server.domain.com/exchweb/bin/auth/owaauth.dll.
If I enable Forms based auth on the exchange 2003 server, login works fine. I do not want to enable forms based auth because although this may
work fine internally, my owa machine is published on ISA 2006 for remote users and per Microsoft, " When ISA Server is being used to publish Exchange Web client access, forms-based authentication should only be configured on the ISA Server computer"
Another thing, why do I always need to enter the domain name \ username prefix when logging in to exchange 2101 OWA ?
In OWA 2003 I can simply enter the username and password, without the domain\ prefix.