forms-based authentication

Forms-based authentication provides a Web logon screen for users to authenticate to gain access to their mailboxes when using Microsoft Outlook Web Access. When you use forms-based authentication, your logon credentials are stored in a temporary cookie. Storing these credentials in a cookie provides a more secure mechanism for ensuring session logout and automatic timeout. The initial user's name and password is still transmitted in clear text, similar to basic authentication. This is why SSL encryption must be used with forms-based authentication. [Exchange 2007]