Logging on to Outlook Web Access

Users can log on to Outlook Web Access using either implicit logon or explicit logon.
Implicit Logon
If the front-end server is configured to authenticate users, users can access their mailboxes by omitting the username from the request, and pointing their browser to their mailbox virtual directory. The usual URL is https:///exchange/. After authenticating the user, the authentication information is used to look up the mailbox associated with the user in Active Directory and the back-end server on which the mailbox is located. The URL is updated with the user name and sent to the correct back-end server. This is known as implicit logon. Implicit logon is useful only for logging on to Outlook Web Access; specialized HTTP clients generally do not use implicit logon.
Exchange 2000 Server SP3 and Exchange Server 2003
Implicit logon makes use of the SMTP domain specified on the HTTP virtual directory to identify the user. Therefore, users connecting to that virtual server must have an e-mail address in their list of SMTP proxy addresses on their object in Active Directory with the same domain.
Exchange Server 2003 SP1
Implicit logon no longer relies exclusively on the SMTP domain specified. All the user information can be gleaned from their logon. Users can use any mailbox Exchange virtual directory to access their e-mail messages.
Explicit Logon
There are a few URLs that users can use to connect to Outlook Web Access. The usual URL is https:///exchange//.Accessing Outlook Web Access using this URL is referred to as explicit logon.
Explicit logon must be used when the front-end server is not configured to authenticate users (for more information about authentication, see Authentication Mechanisms for HTTP) or when a user is attempting to access a mailbox that is not their own but to which they have access, for example, in the case of delegate users.
Exchange 2000 Server SP3 and Exchange Server 2003
When the front-end server receives an explicit logon request from a client, the user name is extracted from the URL and combined with the SMTP domain name associated with the virtual directory or virtual server to construct a fully qualified SMTP address. The front-end server looks up this address in Active Directory and determines which back-end server has the mailbox associated with the address. The front-end server then forwards the request to that back-end server, which processes the request and returns it back through the front-end server to the client.
Exchange Server 2003 SP1
The user can choose to override the SMTP domain configured on the mailbox virtual directory, by specifying the SMTP address in the URL itself. For example; https:///exchange/username@domain.com. If no SMTP domain is specified, the SMTP domain from the virtual directory will be used.
You can prevent specific users from accessing Outlook Web Access by disallowing the HTTP protocol for those users. To change a user's protocol settings, in Active Directory Users and Computers, use the Exchange Advanced tab in a user's properties.
Simplifying the Outlook Web Access URL
Users commonly request that a simpler URL be made available for accessing their mailbox. For detailed instructions on simplifying the Outlook Web Access URL, see How to Simplify the Outlook Web Access URL