How can I send an email to all the users in my application via a trigger? There is currently a facility to select users but what if I need to send the email to all my users?
You can select them all in the trigger definition
The trigger will work perfectly as long as no user is added. So, this would mean that I would have to edit the trigger each time I add a new user?
Yes, this is the simplest recommendation I have at this time.