assuming all emails sent to the clearnet from a specific email provider are tracked by country e.g. all emails from protonmail will have a link to switzerland and the NSA AI will scan and read them cause they are in the clearnet. If protonmail uses a .onion address, does the email exit protonmail servers into the clearnet through a tor exit node? Can the NSA AI track it?
You should slice it into two parts:
Client to server communication
If you want to access the server to send or receive an email, you can use tor and access the hidden service. This has the advantage that an attacker under normal circumstances is unable to see that you have connected with your IP to the server.
Server to server communication
If the server sends an email to another server it uses the clearnet under normal circumstances. The clearnet is used to avoid these emails being marked as spam at the receiving server because almost every tor exit node is on spam blacklists.
Protonmail mails are not send through an exit node. Because of that the NSA might track that the mail is sent from switzerland.
Client_A ---(tor)---> ProtonMail ------> MailProvider_B -----> Client_B
---(tor)-->: Connection via tor
---------->: Clearnet connection, which hopefully uses TLS
Encrypted & meta-data-free alternatives
The following alternatives are relatively new and might have vulnerabilities:
- ZeroNet Mail(https://zeronet.readthedocs.io/en/latest/using_zeronet/sample_sites/#zeromail)