This article provides the steps to configure email notification rules such that users will not receive multiple email messages for the same event.
Tracker will only send one email to a single user for each email notification rule that is triggered (even if the user is on the notification list multiple times). If the conditions for multiple notification rules are triggered at the same time and the notification lists overlap, this will result in multiple email notification messages being sent to some users.
The way that most customers configure the system to avoid multiple notifications for a single operation is to either:
Have rules for "On Edit" and "On Task"
Have rules for "On Change of Status" and "On Change of Assignee"
If you want users to be notified whenever something changes, then using one "On Edit" rule plus one "On Task" rule will send notifications for all changes (you will, of course also need "On Add" and "On Delete" also, but those don't overlap with Change of Assignee or Change of Status").
If the users are to be notified only on the key updates of the issue (e.g. change of status or change of assignee), then the "On Change of Assignee" and "On Change of Status..." rules can be used, but never combine them with "On Edit" or "On Task". As by doing this, no one will receive more than one email notification for a single operation (Add, Edit, Task, Delete).
With the fairly wide range of "substitution" strings now available for the Subject and Operation Description associated with each Email Notification Rule (as well as the many other configurable content options), you should be able to get all the information someone needs into a single email. For instance, if you are using On Edit + On Task rules and you want to highlight the Assignee (the one at the end of the operation), you can simply include the "<assignee>" substitution string in the Operation Description. Yes, the Operation Description (and Subject) line can't be quite as specific for On Edit or On Task as it can for On Change of Assignee (as you won't know whether the assignee changed), but you will avoid the duplicate emails. Your end users may rather have slightly less specific information in the email (e.g. "it was edited and the assignee after Edit is X and the status after edit is Y"), but not get multiple emails for some events (e.g. Edit or Task operations that also change Assignee or Status).
By changing your rules to avoid overlapping conditions that also have overlapping notification lists (avoid having two conditions that can be true at the same time where the notification lists for the two conditions also overlap) you can avoid multiple emails for a single event.
For more information, review the Notifications Help Guide section. Or, for Versions 5.5.4 or older, browse to http://www.nrtracker.com/pthelp55/Admin/help_email_assign.htm