system fields not invoking apex update trigger

Question

I am trying to send an email to the contact owner when the email on contact has bounced. Below is the code, it works and send email to the contact if I remove the IsEmail Bounced condition.

trigger testTrigger on Contact(after update) {
    public Emailtemplate EmailBounced;
    EmailBounced = [select id, name from EmailTemplate where name = 'Email Bounce mail template'];
    for (Contact con: Trigger.New) {
        if (con.email != null && con.isemailBounced == TRUE) {
            Messaging.SingleEmailMessage email = new Messaging.SingleEmailMessage();
            email.setTargetObjectId(con.ownerId);
            email.setsaveAsActivity(FALSE);
            email.setTemplateId(EmailBounced.id);
            email.setSubject('Email Bounced Alert : Email does not exist');
            if (con.ownerId != null) {
                Messaging.sendEmail(
                        new Messaging.SingleEmailMessage[] {email});
                system.debug('email sent ---------');
            }
        }
    }
}

Tried with the workflow but not luck.

Answer 1

@sfdcfox covers this in an 2011 post in the Developer Forum that describes how bounces don't cause normal DML events on objects and hence triggers won't execute.

He suggests the following workaround (which makes sense as when a bounce occurs is asynchronous and hence when the notification occurs to the contact owner can be asynchronous as well)

• Write an Apex Scheduled Job (run daily)
• That queries for Contacts where EmailBouncedDate = YESTERDAY
• And then sets/updates a custom field on Contact such as isReadyForBounceNotification__c to true. This update will be a DML event ..
• That then is picked up by a workflow that sends out an email alert and finally resets the isReadyForBounceNotification__c to false.