You can stop or start the mailer sending emails by selecting the appropriate Mailer function.
Stopping the mailer stops it from sending any messages without closing the mailer down. Care should be exercised when stopping the mailer as it will not accept any notifications from CatTools for queuing when in a stopped state.
You would stop the mailer if you need to change an email message for some reason before it is sent, or if you want to perhaps delete a message from the queue.
Selecting the start function allows the mailer to queue and send messages again.