If you have two separate Exchange Server 2007 mailbox servers, and users in one mailbox server can login to Outlook Web Access using your Client Access Server, while the users on the second mailbox server cannot log in to Outlook Web Access using the same Client Access Servers, the following might help.
This issue is seen if the mailbox server is running Exchange Server 2007 SP1 on Windows Server 2008. From Server Manager, open Web Server (IIS). Make sure the following Role services are added:
Under Application Development, select the following:
- .Net Extensibility
- ISAPI Extensions
- ISAPI Filters
- Server Side Includes
- .NET environment
Under Security, select the following:
- Basic authentication
- Windows Authentication
Do an IISRESET /noforce.
You should be able to login now. If you can’t try logging in using the domainusername format, even if you chose the option for ‘user name only’ on your Client Access Server. If you are able to log in with domainusername and not just username, and you have enabled ‘username’ only option under Forms based Authentication on your Client Access Servers, try the following.
On the IIS of your Exchange Server 2007 mailbox server, navigate to the /exchange virtual directory, open Authentication, and change the properties for Basic Authentication and enter a "" without the quotes for the Default Domain.