The best open source alternative to Mailbird is Thunderbird, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 50 alternatives to Mailbird and many of them is open source so hopefully you can find a suitable replacement. Other interesting open source alternatives to Mailbird are Mailspring (Freemium, Open Source), Evolution (Free, Open Source), Geary (Free, Open Source) and Claws Mail (Free, Open Source).
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.
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Mailspring vs Mailbird opinions
Some users think Mailspring is a great alternative to Mailbird, some don't.
Uses electron bloated framework that consumes many ram
Geary is an email application built around conversations, for the GNOME 3 desktop.
Geary vs Mailbird opinions
pros, cons and recent comments
Unusable for my needs. Can't discard groupment of letters into conversations and delete or move to folder only single letter, not conversation entirely. And it shows only last letters in each conversation, other letters become invisible.
Claws Mail is an email client (and news reader), based on GTK+, featuring Quick response Graceful, and sophisticated interface Easy configuration, intuitive operation Abundant features Extensibility Robustness and stability
Kube is a modern communication and collaboration client built with QtQuick on top of a high performance, low resource usage core. It provides online and offline access to all your mail, contacts, calendars, notes, todo's and more.