[akerl_]

You don't really have to "self-host" (and in fact, I think self-hosting is a recipe for pain and suffering). What I've done personally is:

1. Buy your own domain (ideally not via Google Domains; I use Amazon, but there's plenty of solid registrars).

2. Set up a Google Apps account (I think I pay something in the neighborhood of $5-10/mo, which seems not crazy given how email is the linchpin of every other service)

3. Configure DNS for your domain to point to Google Apps.

4. Pick a backup tool and back up your Google Apps to somewhere. I've got a Synology NAS, so I use its built in tool to back up Gmail/Drive/etc, but there's any number of tools depending on where you want to store the data / how you want to handle retention / etc.

Now, if Google closes your account, you have backups of your data, and you pick a new mail provider and update your DNS records.