PEPS is described as 'open source secure email and file sharing platform' and is an app in the Online Services category. There are more than 10 alternatives to PEPS for a variety of platforms, including Online / Web-based, iPhone, Linux, Android and iPad. The best alternative is ProtonMail, which is both free and Open Source. Other great apps like PEPS are Tutanota (Freemium, Open Source), mailbox.org (Paid), Mailpile (Free, Open Source) and Yandex.Mail (Free).
mailbox.org offers a secure e-mail account for home and business use. The domain name, email@example.com, is easy to remember and can be understood anywhere in the world. They have been operating e-mail accounts for more than 20 years and are a highly reliable service provider.
Mailpile is a modern, fast web-mail client with user-friendly encryption and privacy features. The development of Mailpile is funded by a large community of backers and all code related to the project is and will be released under an OSI approved Free Software license.
Hushmail is a commercial email service focusing on security with features such as industry-standard OpenPGP encryption and two-step verification. All communications also use a secure SSL/TLS connection.