Best Open-Source Email Clients 2026: 6 Options Compared

Open-source email clients fall into desktop apps and webmail you host. Desktop apps, Thunderbird, Evolution, Geary and Mailspring, install on your computer and connect to any IMAP provider, so you keep Gmail, Fastmail or your own mailbox and only change the window you read it in. Webmail clients, Roundcube and SnappyMail, are PHP programs you install on a web server so that you or your users read mail in a browser; they pair with your own mail server or hosting provider. Pick a desktop app if you just want a better inbox on one machine: Thunderbird is the safe default, Evolution suits GNOME users who want calendar and contacts built in, and Geary keeps things minimal. Mailspring has a modern look but its paid Pro subscription unlocks extra features such as read receipts and mailbox analytics, so the free version is the open core, not the whole product. Choose webmail if you run mail for a small organization and want one install everyone shares. Be aware that a mail client never replaces a mail server; you still need an account somewhere. Licences below come from each repository or official page as of the check date.

Thunderbird

MPL-2.0 desktop client for Windows, macOS and Linux with no paid plan stated on its about page. The safest default for most people moving off a webmail tab.

Price: Free (Free and open-source desktop mail client; no paid plan stated on the about page) (Thunderbird pricing, checked 2026-10-23).

Platforms and license: Windows, macOS, Linux. MPL-2.0 (open source) (license source).

Best for: General desktop use.

Mailspring

GPL-3.0 UI and sync engine with a polished look. Mailspring Pro is a separate monthly subscription for extras like link tracking and read receipts; the price was not checked.

Price: Free (Free tier includes unified inbox, snooze, send later, rules and templates) (Mailspring pricing, checked 2026-10-24).

Platforms and license: Windows, macOS, Linux. GPL-3.0 (open source) (license source).

Project activity: 18k GitHub stars · latest release 1.26.2 (Oct 22, 2026) · last commit Oct 27, 2026

Best for: Users who want a modern interface.

Evolution

GNOME's mail, calendar and contacts client, mostly LGPL 2 or 3 by file header. Good if you want one app for all three on a Linux desktop.

Price: Free (Free and open source mail and calendar client) (Evolution pricing, checked 2026-10-24).

Platforms and license: Desktop (GNOME). LGPL-2.0 or LGPL-3.0 by default (per-file headers) (open source) (license source).

Best for: Linux desktops needing calendar too.

Worth knowing: COPYING says code is under LGPLv2 or LGPLv3 unless a file header states otherwise.

Geary

GNOME email client under LGPL-2.1 or later, built to stay simple. Fewer features than Thunderbird, which many users count as a plus.

Price: Free (Free and open source email client) (Geary pricing, checked 2026-10-24).

Platforms and license: Desktop (GNOME). LGPL-2.1 or later (open source) (license source).

Project activity: 395 GitHub stars · last commit Oct 23, 2026

Best for: A minimal Linux inbox.

Worth knowing: COPYING is the GNU LGPL, version 2.1 or later.

Roundcube Webmail

GPL-3.0 browser-based multilingual IMAP client written in PHP. You host it on a web server to give a group a shared mail page.

Price: Free (Free and open source webmail) (Roundcube Webmail pricing, checked 2026-10-24).

Platforms and license: Web, Self-hosted. GPL-3.0 (open source) (license source).

Project activity: 7.2k GitHub stars · latest release 1.7.5 (Oct 19, 2026) · last commit Oct 25, 2026

Best for: Hosting webmail for others.

Worth knowing: README: browser-based multilingual IMAP client written in PHP. License taken from the repository metadata and LICENSE file; description from the project README. No paid plan was checked.

SnappyMail

AGPL-3.0 fork of RainLoop described as simple, modern and fast. Another self-hosted webmail option, lighter than Roundcube.

Price: Free (Free and open source webmail) (SnappyMail pricing, checked 2026-10-24).

Platforms and license: Web, Self-hosted. AGPL-3.0 (open source) (license source).

Project activity: 1.7k GitHub stars · latest release v2.38.2.1 (Oct 23, 2026) · last commit Oct 27, 2026

Best for: Light webmail on small servers.

Worth knowing: README: simple, modern and fast web-based email client, a fork of RainLoop Community edition. License taken from the repository metadata and LICENSE file; description from the project README. No paid plan was checked.

Which one to pick

• You want a better inbox for Gmail or Fastmail on your laptop: Thunderbird
• You run mail for a small team and want a browser interface: Roundcube Webmail
• You use GNOME and want email, calendar and contacts together: Evolution
• You prefer a clean, modern look and accept an optional paid tier: Mailspring