How is disabling the account when it's not being paid for illegal? Beyond some grace period, if I'm not paid, I'm not accepting your mail. If I'm not being paid, I'm not answering DNS queries on your behalf either.

I'm not going to interfere with your contract with a different party that handles your mail or DNS if that's how you manage your mail or DNS.

I'm a nice guy so I'll signal a temporary error and if you arrange payment (or at least claim that you will arrange payment shortly), hopefully your correspondents will retry and you'll just have delays and not lost messages.

DNS is generally prepaid. You can't sabotage services because you aren't being paid. For example, a landlord can't disable someone's prepaid internet when he stops receiving their rent.

The remedy for failure to pay is to seek payment or sue, not to sabotage the client's business.

So if you paid me Jan 1 2025 for one year of DNS service and now it's Jan 1 2026 and you didn't pay me again, I'm supposed to keep serving your DNS?

If the money runs out, the service turns off. That's not sabotage anymore than the phone company turning off your phone or the electric company turning off your power. Although phone and electricity may have regulated shutoff procedures.

That's not the scenario being described here. The registrar would handle all of that and release the domain if it weren't paid.

I didn't say anything about the legality... They asked how to block email. Both of these would work.

There's no reason to respond to questions or points nobody is making.

You don't think there's a reason to say someone's illegal advice is illegal? OK.

How would it be illegal if it was, for example, explicitly listed as an option in the contract?

No, because I have no idea what jurisdiction the person lives in, nor what the contract says.

Why would I respond to something they didn't ask? Why would I give legal advice when I'm not a lawyer?

Start responding to things that are asked, not what you'd prefer to debate.