Hi! You can't use a public domain. You need to use a private domain, an email associated with it, and access to that domain's host. For example, my domain is sender.net. To be able to verify my domain, I need a domain-attached email address like michael@sender.net, support@sender.net, and so on.

In most cases, if you already have a website and a domain, you should be able to acquire an email address with your domain, so you do not use a simple @gmail.com email address for your business endeavors. Domain providers often allow you to have an email address with your domain name.