RainLoop

Category: Email Clients.

MIT🖥️ Self-hostable

Mailpile

Category: Email Clients.

AGPL-3.0-or-later☁️ Hosted only

SnappyMail

Category: Email Clients.

AGPL-3.0🖥️ Self-hostable

Roundcube

Category: Email Clients.

GPL-3.0-or-later🖥️ Self-hostable

K-9 Mail

Category: Email Clients.

Apache-2.0☁️ Hosted only

Evolution

Category: Email Clients.

LGPL-2.1-or-later☁️ Hosted only

Mailspring

Category: Email Clients.

GPL-3.0☁️ Hosted only

Thunderbird

Category: Email Clients.

MPL-2.0☁️ Hosted only