Which is the privacy of onion mail and ch or org or io domain?

I’m looking for a free email provider that is anonymous and privacy oriented. So the question is, which is better, closed source email for onion domains or open source emails for national domains like Protonmail, Tutanota and Disroot? I heard that the anonymity is the best domain, but it is a closed source, so the administrator may see it or contain a virus. Protonmail is open source, but there may be information disclosure in the national domain. Which is better?
Also, I want to use it with Thunderbird, so please let me know if you have a good email provider that supports SMTP, MTSP.POP3! !

3 posts were merged into an existing topic: Which domain or country has the most privacy?