S/MIME

S/MIME adds end-to-end encryption and digital signatures to email using X.509 certificates. Signatures prove who sent a message and that it was not altered, while encryption keeps contents private even from mail servers. It is common in government and regulated industries where certificate infrastructure already exists.

• Proton Mail → Encrypted email from Switzerland with PGP built in, no key wrangling required. End-to-end encryption only applies Proton-to-Proton or with PGP contacts; mail to ordinary inboxes travels like ordinary email.

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