This is page was revised on 10/07/2020 to use Ajax/REST, and on 11/10/2020 with a revised format for the message content. Please test this using the preview facility and also simulate sending emails using the test site. You will receive a copy of each email, so maybe start with a friendly tower or too? A version with the original content is here!
When you do send emails, you should see the buttons uncheck as they get sent one at a time. And it may not be a good idea to display all letters at the same time.