The free basic account means you can try it out at no cost, but you must upgrade to the Pro plan to unlock features like custom filters. ProtonMail is one of the most polished secure end-to-end encrypted email services on the market. It lacks mobile clients but includes a full suite of web-based email, contacts, cloud storage (opens in new tab), and calendar office apps. If you like ProtonMail’s modern interface, (opens in new tab) is another secure email provider that’s easy to use. It also offers a fully-encrypted calendar and support for U2F two-factor authentication. You may prefer ProtonMail’s adherence to open-source standards, but while ProtonMail doesn’t encrypt your email subject line, Tutanota does. If security is your highest priority, Tutanota (opens in new tab) is a German secure email service that uses its own encryption standards. Two-factor authentication is supported (Image credit: ProtonMail) The competition Overall, it’s an impressive level of security for emails. You can enable two-factor authentication (opens in new tab) so no one can access your account without also having access to your mobile device. There’s full support for PGP, and the encryption algorithms used are open-source versions of RSA and AES. The code for the web client and encryption algorithms are all open-source (opens in new tab), so any security issues can be patched quickly. In terms of physical security, ProtonMail’s IT infrastructure (opens in new tab) resides under 1,000 meters of granite rock and your data never goes to the cloud. However, the email subject lines are not stored in an encrypted format, so if compelled to by a Swiss court order, ProtonMail could turn over the subject of your emails to the authorities. ProtonMail uses end-to-end, zero-access encryption for your emails, so they are always encrypted when in transit or when stored on the email servers. ProtonMail has a comprehensive knowledge base (Image credit: ProtonMail) ProtonMail: Security

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