We have Exchange 2007 set up with Outlook Web Access. ASP.NET forms authentication is enabled for the OWA directory and all other authentication methods are disabled. When browsing to the OWA site I get the login form, as expected, however when trying to log in I always get "The username or password that you entered is not valid. Try entering it again." I'm sure that the username and password are correct. I've already tried it both with and without the domain name, ie. "DOMAIN\username" and just "username". How do I troubleshoot this?
Figured it out. We had to go to Exchange Management, Server Configuration, Client Access, Outlook Web Access tab, open the owa web site, Authentication tab and select "Use forms-based authentication". After that OWA still logged an error, saying that the authentication type in Web.config should be set to "Windows". We had it as "Forms", which seems correct, since we are logging in through a web form. Nevertheless, changing it to "Windows" in Web.config file did the trick.