Cross-platform organizer + email client?

Question

Fonts

Tell me some good cross-platform, open, mail client with an organizer function, with the removal of the database into a separate file and support for windows, linux, android and possibly ios.

Answer 1

https://alternativeto.net/software/mozilla-thunderbird/

Answer 2

https://www.essentialpim.com/en/

Answer 3

Only a webmord. Keyboard-and-mouse-driven desktops and fingertip-driven mobile systems take very different approaches. Even FF for android is actually a completely different product, in which only the name is from FF. And in the mail client, the user works much more than in the browser. Therefore, all of the above can be combined only with a web muzzle.