When you try to send e-mail messages to recipients from certain domains, you may
experience the following behaviors:
- The e-mail message is not delivered and you receive a non-delivery report
(NDR) that contains error code 5.0.0.
- The number of domains that you cannot send e-mail messages to increases.
- You notice one or more of the following events in the Application log of the
Event Viewer:
http://support.microsoft.com/default.aspx?kbid=300580