Open source Email clients

Balsa

Balsa is a lightweight e-mail client for GNOME. (GPL)

Linux - FreeBSD

Claws Mail

Claws Mail is an email client (and news reader), based on GTK+. (GPL)

Linux - FreeBSD

Evolution

Evolution provides integrated mail, addressbook and calendaring functionality to users of the GNOME desktop. (GPL)

Linux - FreeBSD

Geary

Geary is a new email reader for GNOME designed to let you read your email quickly and effortlessly. Its interface is based on conversations, so you can easily read an entire discussion without having to click from message to message. (LGPL)

Linux

Kontact

Kontact is a personal information manager and groupware software suite for KDE. (GPL)

Linux - FreeBSD

Mailspring

Boost your productivity and send better email with Mailspring, the best mail client for Mac, Linux, and Windows! Mailspring is a new version of Nylas Mail maintained by one of the original authors. (GPL)

Linux - Windows - macOS

N1

N1 is an open-source mail client built on the modern web with Electron, React, and Flux. It is designed to be extensible, so it's easy to create new experiences and workflows around email. (GPL)

Cross-platform

Sylpheed

Sylpheed is a simple, lightweight but featureful, and easy-to-use e-mail client (mailer, MUA). (GPL)

Linux - FreeBSD - Windows - macOS

Thunderbird

Mozilla Thunderbird is a free, open source, cross-platform e-mail and news client developed by the Mozilla Foundation. (MPL)

Linux - FreeBSD - Windows - macOS

9 applications