Here are a few issues I have not seen mentioned.
If SMTP, under SMTP configuration try leaving the Sender Name field blank and only use the Sender Address field.
If you are using SMTP notifications, has the setting for Annoymous email under protocol been changed? If so, it may be looking for authentication before allowing the notification in.
Also, with SMTP, if you are testing with Outlook Express with an exchange server that has been rebooted make sure the Pop3 service has restarted. It is disabled by default, so if someone turned it to manual and rebooted the server it may not be running.
Netsend recipients are tied to the Messenger service, so make sure that is on for all servers involved.
A very likely culprit can be the option to limit notifications sent to each recipient. That is a "circuit breaker" and is easily set incorrectly. With that set incorrectly, you could have situations that clear up after many days, send a few notifications, then be blocked for many days again... If in doubt on to how to setup the feature, disable it. This option is located on the recipient properties screen. If you do have it set, be sure to check the setting for "Reset" so notifications will begin again.
Also, be sure the account you are using actually has rights to a mailbox and that mailbox is not hidden.
As stated above in another post, also recycle the BE services.
Message Edited by D B on 07-11-200710:38 AM