How someone get off GMail if they have already been using it for a decade or quite a few years more than that? Has anyone done this? How do you do that with the fewest issues possible?

Having the most important communications with other people and companies, and the login verification all in the hands of one company which could shaft your access in all sorts of ways (screw up, removing service, ban) is just terrible in the long term. And if someone is using their ISPs email address, that is something that would keep them signed to that ISP even though another may offer a service much better for them.

Anyway, anyone migrated away from their email provider after a long time signed up and could answer some of the questions in the first paragraph? Thanks.