Apps similar to Private.Ki include Proton Mail, which is open source with a free version. Other options are Tuta Mail, Disroot, Zoho Mail and Posteo. WebMail Providers like Private.Ki are a crowded field, with more than 50 alternatives for the web, iPhone, Android, iPad and Mac.
Galae is a secure email service focused on deliverability, self-management and interoperability. It totally relies on free/libre opensource software.
OnionMail is an anonymous and encrypted mail server made to run on the TOR network without losing the ability to communicate with the Internet.
Virtru provides digital privacy technology to let you easily share information securely through all major email programs and applications. Virtru puts you in charge of how your digital information is shared.
Finally, an email service that's built around your privacy. Get your @criptext.com email address and see what it's like to have peace of mind and privacy in every email you send.
United States
Countermail is a web-based email service. It is hosted in Sweden. Its focus is on privacy. It provides several features, such as PGP support and diskless servers to protect users ability to communicate securely and anonymously.
Sweden
EU
Encrypted email inbox with calendar support, tasks, notes, bulk import, search features, key storage, encrypted cloud storage, file sharing.
SafeSwiss The world’s most effective end to end encryption security solution including P2P Voice, encrypted email, encrypted storage, ephemeral text chat, docs share & group chat for mobile phone devices and PC's.
Switzerland
MeSign is a free email encrypted client. Once you log in to your email account with MeSign App, the free S/MIME certificates will be issued, installed and configured automatically. The users can start to encrypt within 3 minutes.
China
Unofficial ProtonMail extension. Provides notifications and makes it possible to close the ProtonMail tab, and even the browser, without getting logged out.
Mailture, a secure, business-oriented email service, is made to cater to all your emailing needs. With top-notch collaboration and communication features, Mailture offers much more than your usual inbox.
United Kingdom
Providing HIPAA-compliant email, secure email & web services since 1999. Secure communications via email, text, chat, video, and web.
France
