Email alarms can be configured in the AS and ES and understanding that interaction is needed
Windows Server 2008
There is a need to know what happens when creating email alarms in the AS and ES
The server (AS or ES) that has the email notification object will send the email. So if you want to be sure that the AS alarms still send emails even if the ES is offline, then you should have email notifications configured on the AS and not rely on a global email notification on the ES. If notifications are configured on both the ES and AS which triggers on the same alarm, then two emails will be sent. One when its triggered on the AS and one when the ES fetches the alarm from the AS.
You may be able to manage the triggering of the AS alarm by a program that checks the online status or alarm indication of the ES being offline.