The best open source alternative to FairEmail is Thunderbird. If that doesn't suit you, our users have ranked more than 25 alternatives to FairEmail and 16 is open source so hopefully you can find a suitable replacement. Other interesting open source alternatives to FairEmail are K-9 Mail, Betterbird, Evolution and Delta Chat.
Cross-platform email client supporting multiple identities, chat, and strong filtering. Extend functionality with add-ons like RSS/Atom feed readers and PGP support.
K-9 is an open source email client for Android with multi-folder sync, email signatures, Bcc-to-self, return-address configuration, keyboard shortcuts, Exchange Support, message flagging, IMAP deletes, saving attachments, configurable notifications and more.
Betterbird, a soft fork of Mozilla Thunderbird, improves user experience with advanced features, bug fixes, security patches, and multi-row descriptions similar to Outlook. Compatible with multiple platforms and can be used alongside Thunderbird, sharing the same profile.
Evolution is a personal information management application that provides integrated mail, calendaring, address book and task list functionality.
Provides a chat experience over email, with all messages and contacts stored on user devices, open source code, group media support, and compatibility with any provider. No central servers, no tracking, works without SIM, and can be used by anyone just via email.
It is not email, it is a messaging app.
Delta Chat is a messenger, not an e-mail application.
Boost your productivity and send better email with Mailspring, a beautiful, fast email client for Mac, Windows, and Linux. Mailspring is free to use and an optional pro version adds read receipts, send later, reminders and more.
Email and news client on GTK+ foundation featuring quick performance, extensible plugins, secure protocols, advanced filtering, strong folder and contact management, lightweight design, powerful search, customizable interface, multi-language support, and encryption.
Privacy-focused Swiss email system provides 20 GB free storage, supports custom domains and unlimited storage, syncs contacts and calendars, is ad-free, and is part of a secure productivity suite used by over a million users across Europe on all devices.
No-frills, easy to use, easy to maintain Email client for Android based on the JSON Meta Application Protocol (JMAP).
Eclipse Mail is a fork of Interlink Mail and News made for Windows XP and runs on IA-32 i686 platforms. Some advantages over upstream and roytam1's mailnews are more optimizations and better interoperability with upstream.
LucaMail is an open source, cross-platform email client. LucaMail is developed to provide cross-platform alternative to Email Clients that are really exists. LucaMail focuses on modern technologies as well as maintaining a user-friendly UI.
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Fairmail is based on K-9 and is more user-friendly