[manytimesaway]

"How to become unbannable"

Step 1 : go with the one company that's known worldwide for abusive & permanent bans with no recourse.

This post is a bit too generic, but it's true that using your own domain for mailing is the best solution to avoid getting locked out. Although you need to pick a good registrar, too...

[morshu9001]

well your recourse is repointing the domain

[xp84]

It's worth pointing out just in case someone might forget/not think of it... Don't register your domain or DNS with Google Domains / GCP if you host your email with Google Workspace... since if you get locked out of the Google account you could be unable to update your DNS.

The saddest thing though is that in some ways Gmail is harder to hack into than some registrars. I remember a postmortem write-up from a guy who had his personal domain easily hijacked by social engineering someone at the domain registrar, which then served as the foothold of a larger identity theft attack against him. Google, by virtue of simply not even doing customer service, is much harder to social engineer, so the author of that piece pointed out that ironically if he'd put more of his eggs in the GOOG basket, he'd have been safer.