Cock.li

The service has onion addresses for both login and registration, but attempts to create a new account via onion usually result in errors like "too many accounts". Registration over Tor via a clearnet address works fine, though.

New accounts can receive emails without restrictions, but it's required to solve a one-time proof-of-work challenge to enable sending emails. The challenge usually takes a few minutes to complete. PoW runs in the background inside your browser, so you don't have to do anything. However, PoW requires JavaScript enabled, but you can also download a provided python script and solve the challenge locally if you don't mind installing pip packages. Don't forget to confirm with your AI that the script is safe to run.

Cock.li has different domain names, but most of them are flagged by slave tech services as disposable email domains with high risk of abuse, so if you simply need to receive an activation code, then consider using temporary email services instead since they often rotate domains.

Every email service provider is a honeypot because it's an account based centralized service controlled by one officially registered compliant entity that either already fully leaked its database or will leak it soon due to coercion and hacks. You should never use emails for anything important. If you must use a centralized email service, then minimize your metadata leakage with Tor and encrypt messages with PGP.