Faster UX for message previews

When sending a preview email for a newsletter

• if I add a new, unknown recipient for the test email, it is only saved after the test email is sent successfully. Wouldn't it be better to store it immediately in order to spare me another copy/paste?

• when I add a customer ID to that same popup, it disappears after a successful send. Wouldn't it be better to keep it until the window is closed? (session storage)

• same as the above, for the case where the sending fails