You might want to have a look at the Trigger Threshold tab of your Trap Rules to limit the number of emails sent for a specific Trap category.
Here is the description from the Administration Guide:If you want to suppress alert actions until a specified number of traps arrive that match the rule, click Trigger Threshold, check Define a Trigger Threshold for this Rule, and then enter option values as appropriate.Note: When Suspend further Alert Actions foris checked, alert actions are not sent until the specified amount of time has expired. Once the time period has expired, only new alerts are sent. All alerts that are suppressed during the time period will never be sent.
Not sure if this is what you are looking for...but it might help.