Insert your modification logic
At this point you need to determine what it is you are planning to modify. The plugin provides you with a pointer to the JMailQ mail object.
The sample plugin checks to see if the from address is a mailing list and if so changes it to noreply@.
Make sure you return a false in the $event->setArgumant() function call as shown in the sample to drop the email. If you return false the email will be dropped.