Quest Intrust Server real-time email alerts may stop functioning (the specified recipients do not receive real-time email alerts into their mailboxes).
The following error logged in the Intrust event log: "Notification for rule %RuleName% failed. Error text: SMTP error: 501 5.5.4 Invalid Address."
The real-time policy has been assigned the email notification group that includes another notification group (nested notification group).
Avoid creating nested notifications group, include only notification operators into the notification groups.