XCLN: Routing Restrictions Require SMTP Authentication

When an Outlook user tries to send an SMTP message to a recipient outside of his or her organization, he or she may receive one of the following error messages: The sender can receive this message either in a non-delivery report (NDR) or in dialog box stating that "Relaying is Prohibited." The error or NDR notification are dependant on which e-mail program the sender is running.

Service Pack 1 for Exchange Server 5.5 includes functionality to stop the relaying of spam SMTP messages through a site. The Internet Mail Service can be set to enable the Reroute Incoming SMTP Mail option, and can have the Routing Restrictions specified as Hosts and Clients that successfully authenticate. In this case, the Internet Mail Service will be able to route mail, then the Outlook client MUST authenticate before outbound mail will be sent. Without the client sending either the proper POP3 or IMAP4 authentication commands, the Internet Mail Service will deny delivery in accordance with the Routing Restrictions settings.

To enable client authentication on:

Outlook 97

Outlook 97 uses a POP3 service account, and does not have the ability to designate a separate Inbound and Outbound mail server for receipt and delivery of messages. In this case, all that is required for authentication is a valid account name which can be found in the Mailbox Information section of the Internet Mail Service for a users' specific profile.

NOTE: Adding the Internet mail enhancement patch for Outlook 97 allows secure password authentication. The filename is Outlimep.exe; file size is 491 KB, and it is available at:

Outlook 98

1. From Control Panel, double-click Mail, or Mail and Fax.
2. Select the appropriate Profile, and click on Properties.
3. Select the Internet Mail Service, and click on Properties.
4. Within the Servers tab at the bottom of the dialog box, select the My Server Requires Authentication check box. By clicking on the Settings button, you will be able to:
   
   
   1. Select whether you want to use the same credentials you used when logging onto Exchange Server, and
      
      
      1. Add a different set of credentials.
         
         -or-
      2. Use SPA (Secure Password Authentication).

Outlook Express

1. Start Outlook Express.
2. On the Tools menu, click Account, and select the Mail tab.
3. Select the profile that you wish to change, and click Properties.
4. Within the Servers tab at the bottom of the dialog box, select the My Server Requires Authentication check box. By clicking on the Settings button you will be able to:
   
   
   1. Select whether you want to use the same credentials you used when logging onto Exchange Server, and
      
      
      1. Add a different set of credentials.
         
         -or-
      2. Use SPA (Secure Password Authentication).

For additional information, please see the following article in the Microsoft Knowledge Base: