This article briefly explains why the following error, or similar, may occur when using alerts for Engineer's Toolset in NPM.
2916 The transport failed to connect to the server. Error Number -- 2147220973
When an alert/action is configured within NPM for ETS to email when a node or interface is down, the receiving
SMTP server should also be configured to allow incoming SMTP relay sessions to be able to forward
the action email alert.