This option lets you set the type of access (anonymous or authenticated) that people have after they log on to Outlook Web Access. To make this choice, click Anonymous or Authenticated.
With anonymous access, users are not prompted for logon information or their Microsoft® Windows NT® credentials, and they have access only to the public folders that have had "anonymous" permissions enabled. Anonymous logon provides the ability to make a folder accessible to people who are not defined within the Microsoft® Exchange organization. A typical example of this is a folder that acts as a repository for a newsgroup or a discussion and has been made accessible on the Internet, where prospective users are not known by the person hosting the discussion.
For the authenticated option, users are prompted to provide credentials when they log on, and they can access any folder they have permissions to. Use this option if you want users to be able to access their Inboxes. You can also use this option to make a public folder accessible only to an explicit list of users who have already been defined within the Microsoft Exchange organization. Additionally, these users can be given a highly granular level of permission to the particular folder. For example, some might be given Author permission while others are given only Reader permission.