The client for mail services was released with through encryption. The new version of ElectronMail 4.0.0 removed support for the service Tutanota, support left Protonmail. The program was written by Vladimir Yakovlev on the framework Electron and is open source (MIT license).
The main difference from the free versions of official clients is the ability to search, the absence of volume restrictions and additional offline features. Package builds are available for many distributions (deb, snap, freebsd, pacman, AppImage, rpm, dmg). For users tutanota compiled unsupported assembly tutanota-mail 4.0.0. The reason for the removal of Tutanota support from the main ElectronMail code is the emergence of a fully functional official client service.
Source: linux.org.ru