

The only reasonably future proof solution is to get your own domain, and redirect emails sent to @yourdomain.com to your email provider.
Then you can freely change providers in the future but your email addresses stay the same. Doing that costs very little and doesn’t require any self hosting, just buying a domain. Looks professional too.



No, your emails are still sent from your providers servers and are signed by Proton/Tuta/Gmail/whatever you choose to use. Your domain is the from: field but it was sent by the actual email provider with all the trust behind it.
I never ran into something requiring a Google/Apple address. Some may require a Google account, but you can create a Google account with any email address. You don’t actually need to use Gmail on your Google account.