http://dwltorbltw3tdjskxn23j2mwz2f4q25j4ninl5bdvttiy4xb6cqzikid.onion/email-providers/protonmail
Protonmail supports PGP and abides by strict no-logs policy. Back in 2017, the email service provider had introduced Proton Mail Contact, which is a zero-access encryption contacts manager. It uses digital signatures for verifying the integrity of the contacts data.