One thing I've not seen mentioned when people talk about moving to an owned domain is what happens when you don't own it anymore?

There are a million services that assume that if you have access to the email content you are the account holder. Google claims they don't recycle email addresses, but if you lose your domain, the next owner has access to all emails from that point forward.

If something happens and you're unable to renew your domain, are your next of kin out of luck?

> If something happens and you're unable to renew your domain, are your next of kin out of luck?

I'd say "don't do that". I had a friend pass which I knew had a custom domain for email, I told the relatives they had to be on the ball regarding renewal.

At least my registrar will keep sending invoices for a few months without letting go cough cough, so should be enough time to get the certificate of probate. With that the heirs should be able to get the invoice so they can pay.