Fixing Outlook Web Access login error with Exchange 2003 SP2

I today ran into an issue with Microsoft Small Business Server 2003 SP1 (SBS 2003) and Exchange Server 2003 SP2 that I couldn't immediately solve. The problem was that all users were unable to login to Outlook Web Access (OWA) hosted by the SBS server on a LAN.

Even with administrative privileges, user's got the following error message when trying to login to OWA with their browsers:

You could not be logged on to Outlook Web Access.
Make sure your domain\user name and password
are correct, and then try again.

Now, I initially thought this would be a security setting/permission issue, but since even the domain admin couldn't log in, I decided to investigate elsewhere. On the Internet, I found Microsoft KB article 843539 that provided the hints, and the rest I found by using Google Groups.

The reason was that the SBS server was running IIS that had SSL enforced. However, Exchange Forms-based authentication doesn't work with SLL connections, and you have to disable Forms authentication to give proper access to users.

To do this, first go Exchange System Manager, and then navigate to Exchange Virtual Server properties (Servers/Protocols/HTTP), and then clear (uncheck) the Enable Forms Based Authentication checkbox. That should do the trick.

And, if the problem still persists, make sure you've given enough file system (NTFS) rights to the Exchange virtual directory. Open the Security tab for the directory either using Windows Explorer or IIS Manager, and make sure the "Domain Users" group (or similar) has Read, List Folder Contents and Read & Execute rights.