What email do you use with domain registrar? I ended up switching most if mine domains to google domains simply because i find its ui more convenient for me, all eggs in one basket i guess. But how do you ensure that you aren’t gonna loose access to your domain account?
Given the way Google locks out accounts with no support or appeal I can't think of a worse registrar to use.
I use my ISP's email address with my registrar, if they want to keep getting paid each month its in their interests to keep that email address working.
At this point some government entity should provide a way to have an inalienable electronic address. There are strong protections for regular mail, that ensure that mail gets delivered. Cell carriers are required to port numbers. Since email addresses are tied to domain, there should be some usps-like service that allows to have an address, that can be related to a provider of your choosing. And this address is tied to your identity, which you can verify by physically visiting usps or dmv if all else fails.
Email is intrinsically an unreliable service, and always has been. It's a "best-effort" service. But at least email is honest about it up-front, and tries to address reliability in the RFCs.
That was in reference to regular mail. USPS was one of the first fed agencies and mail was one of the few original functionals of the central government. On top of USPS being one of the largest agencies, there is also legal protection against tempering with mail and usps has its own enforcement branch.
In case of email, it probably should simpler. Gov only serves as an address book, essentially. But does minimum of tech implementing it. Given how domain MX records work, does not seem possible. So i think email relay is the closest thing.