Which literally puts you on all autoreject spam lists because SPF and DNSSEC. Unless you pay for GSuite and/or your mail provider allows this custom domain functionality.
The point is, when you switch your phone operator, you don't have to pay the previous operator, in perpetuity, for the privilege of using your number without your calls being blocked.
Yeah but most people aren't paying for g-mail. It's like if you were using T-mobile "free" plan where you don't have to pay anything but you get a number that starts with "TMO", and then getting mad when you can't transfer your free number to Verizon because T-mobile refuses to transfer it.
...Or are they, except not in cash? :) Jokes aside, that's a fair observation, but then one should be able to "transfer" their address by paying a one-time fee, rather than getting a GSuite subscription.
True, email addresses ideally should be more like phone numbers where they are not tied to a specific corporate-owned domain (i.e. "gmail.com"). We would need some sort of standardized lookup though to support such a system.
SPF is trivial to set up for people who already have their own domain; it's literally 1 DNS TXT record.
I'm not aware of any mail providers that require DNSSEC. Were you thinking of DKIM? That's just 1 more TXT record (to publish the public key used to verify the signature), and some mail signing software if your mail server doesn't have that feature built-in (which is freely available).
