If so, how do I do so without interfering anything? Because this not only ease the entire process but also helpful for the email users. And also, is it possible to block off the rest of the subdomains that displays “this is a mail-in-a-box, take control of your email at https://mailinabox.email/”? Perhaps redirecting the user to yourdomain.com as well.
I would probably be open to having a subdomain like mail.yourdomain.com as an alternative. Perhaps rerouting the users that visit yourdomain.com to mail.yourdomain.com until we have a landing page visible.