The most popular alternative is K-9 Mail, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 50 alternatives to Thunderbird so hopefully you can find a suitable replacement. Other interesting Thunderbird alternatives are eM Client (Freemium), Evolution (Free, Open Source), Microsoft Office Outlook (Paid) and Claws Mail (Free, Open Source).
- Open source Android email client with support for multi-folder sync, keyboard shortcuts, and more.
- eM Client is a full featured e-mail client with a modern and easy to use interface. eM Client also offers calendar, tasks, contacts and chat.
- Evolution is a personal information management application that provides integrated mail, calendaring, address book and task list functionality.
- Part of the Microsoft Office Suite, Outlook is a personal information manager that lets you manage your e-mail, calendar, contacts, and tasks.
- Claws Mail is an email client (and news reader), based on GTK+, featuring Quick response Graceful, and sophisticated interface
- Mailbird is more than just another email client - It's an all-in-one communication platform for email, contacts, calendar, apps, task management, video meetings and much more. Try it free, today.
- Free, open source and cross platform messaging and emailing app that combines common web applications into one.
- Geary is an email application built around conversations, for the GNOME 3 desktop.
- 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.