What part of that thread am i saying the opposite?
when the form submits, it will send the emails.
While the emails are being sent, it will stay on the form page. when the emails are done sending, the form page will redirect to the success page. how long that redirect takes depends on how long it takes to complete sending the emails.
if the user would rather not view the page while the emails are sending, they can close the page, the process has been started on the server, so will continue until it is done, although since the page was closed, it wont open a success page.