In a large environment the customer can have different regions each managed by their own Notification Server, so each server has there own group of computers according to the region where those are located.
Why would a computer from one region point to a server from another?
There are many ways to approach this issue. One thing that you can try first is to check the Agent logs and identify when exactly it occurred in one of the computers. You may see in the Agent log when the client machine received instructions on changing the Notification Server name.
You could also check the Altiris Agent configuration (Configuration Tab/Altiris Agent). Sometimes the Altiris Agent Installation Policy can be enabled in all Notification Servers.
If the Notification Server has references or discovered computers that are managed by another Notification Server, it can cause that each regional Notification Server sent the Altiris Agent to client computers from another region (since those are part of the same network) has to this Notification Server it appeared that those computers needed the Altiris Agent. This can cause a lot of computers are redirected to another Notification Server.
If this is the case in your environment: