First things first: (Parenthesis) From now on, if it is important, pay for it. At least a smaller email provider with real human support, but best is "buying" your own domain and hosting your email. Same goes for backups. And pass the info to your loved ones. Less importantly: Since you know exactly what phone# is requested, try to contact it. Approach it in a way that doesn't alarm the renter and blocks you. Meanwhi…
I wish this were still the case. Sadly, if you buy a domain and host your own email, you're going to get stuck in spam filters all the damn time. Your email address will feel broken, sending messages into the void.
The only email infrastructure services that are reasonably reliable belong to the likes of Google (Workspace), Microsoft (365), etc. Protonmail is reportedly okay, but my experience is that they still get spammed an awful lot.