OK, I think the other reply missed your question (if I am reading this correctly).

Basically, if you register your domain through namecheap, then after setting up email at *@ximeng.net, don't update your email address to be [email protected] when changing the rest of your accounts. Reason being, if for some reason there is a problem with the domain, you don't want your only means of fixing that problem to potentially be invalid.

Therefore it wouldn't be a bad idea to keep the account associated with your registrar still on the original Gmail address (or if you are really paranoid, create a new email address through someone like protonmail just for your registrar account).

Right, that is what I meant - you’re then pushing the risk to the management of that secondary protonmail or gmail account. So you basically always rely on a third party to manage the registrar account.

Oh I see. I agree that it is a risk, so - in the vein of another advice in this thread - if you have a co cern about third party email provider, update your domain records to another provider.

Not sure I understand the question.

I have to manage a domain and have a basic understanding of how DNS works, that is unavoidable.

DNS is a bit complicated to describe in short reply but on a very high level: say I register a domain example.com. Registrars usually give you an interface to manage DNS where you can set A records (association with IP), you basically put there 2-5 IP addresses of the DNS servers serving your domain. You can also setup MX records that are used to resolve mail servers for your domain. Setting up fastmail is simple: you tell them that you want them to serve mail for example.com and setup couple of MX records pointing to the Fastmail servers (they give you the full host names).

Sorry I wasn’t clear - basically my concern was that you still have a dependency on a third party email address.