I’ve been thinking about this problem from the other side of the fence: what if I use the provider’s domain and the provider goes away? Not likely in the case o

I’ve been thinking about this problem from the other side of the fence: what if I use the provider’s domain and the provider goes away? Not likely in the case of Gmail, but I use Proton Mail, and frankly don’t entirely trust them not to disappear overnight. Or ban me due to some automated AI decision I can’t appeal.