Mozilla Thunderbird

Mozilla Thunderbird is a free and open-source tool that helps people manage their emails, calendars, and contacts. It also lets users read news updates, chat with friends, and more. Thunderbird is run by MZLA Technologies Corporation, which is part of the Mozilla Foundation. People around the world help create and improve Thunderbird, and they choose leaders to guide the project.

Thunderbird works on many types of computers and devices. You can use it on Windows, macOS, FreeBSD, Android, and Linux. It was built using ideas from Mozilla's Firefox web browser, making it easy and reliable for many users.

Overview

Thunderbird is a helpful tool for managing emails, news feeds, and instant messages. It also includes a calendar and can be customized with extra features through extensions. Users can change how Thunderbird looks with different themes.

Starting in 2022, the Android app K-9 Mail was taken over and plans were made to rebrand it as Thunderbird for mobile devices. In October 2024, the first version of Thunderbird for Android was released, and updates continue to improve it. Thunderbird for Android can be downloaded from Google Play and F-Droid.

Email features

Thunderbird helps manage many email, newsgroup, and news feed accounts. It offers tools like quick search, saved search folders, and message filtering to organize and find messages easily. It supports common email standards such as POP, IMAP, and LDAP, and includes features for secure emailing using encryption and digital signatures.

Thunderbird works with OAuth for safer logins, especially with providers like Gmail and Outlook. It allows linking large files to online storage services instead of attaching them directly. Users can format messages with HTML and use special text effects. Security features include secure connections, encryption, and options to block remote images and certain types of content. The French military uses Thunderbird and helps improve its security.

Other features

Thunderbird is not just for email—it can also gather news and blog updates, called News Feeds and Blogs. It works with RSS and Atom formats.

The program includes a chat feature for instant messaging, supporting IRC, XMPP, and since version 102, Matrix. It has also worked with the Odnoklassniki network, and in the past supported Twitter, Google Talk, and Facebook Chat.

Thunderbird can also read news from Usenet using the NNTP system. Starting with version 91, Thunderbird can show PDF documents right inside the app, so you don’t need another program to view them.

Cross-platform support

Thunderbird can be used on many different types of computers. You can find versions for Linux, Windows, and macOS.

There are also unofficial versions for FreeBSD, NetBSD using pkgsrc, and OpenBSD. Older versions work on OS/2, such as ArcaOS and eComStation.

You can also get the source code and build Thunderbird to run on many other systems.

Android and iOS versions

In June 2022, the Thunderbird team announced plans to create a version for Android devices, working together with the developers of an existing app called K-9 Mail. They aimed to change K-9 Mail into Thunderbird for Android, updating its features and look.

By October 30, 2024, the first stable version of Thunderbird for Android, called Thunderbird Mobile, was released as version 8.0. You can install it from Google Play and F-Droid. The team originally planned to keep supporting K-9 Mail for about a year after launching Thunderbird Mobile, which would be around October 2025.

On May 6, 2025, version 10 of Thunderbird Mobile and the beta for version 11 were released.

As of 2025, an early version of Thunderbird for iPhones and iPads was available through Apple's TestFlight service.

Release compatibility

Legend:

Unsupported

Supported

Latest version

Preview version

Future version

Unofficial ports

History and development

Thunderbird started as a project called Minotaur, right after another project named Phoenix, which later became Firefox. At first, Minotaur didn't get much attention, but when Firefox became popular, people wanted an email tool to go with it. So, Minotaur was revived and renamed Thunderbird, using the same technology that Firefox used.

On December 7, 2004, Thunderbird version 1.0 was released and quickly gained popularity, with over 500,000 downloads in just three days.

From version 1.5, Thunderbird was developed separately from other Mozilla tools, allowing users to choose their own combinations of applications. In 2004, a project called Lightning was announced to add calendar features to Thunderbird.

On July 26, 2007, Thunderbird became its own project, separate from Mozilla's main focus on Firefox.

In 2011, Thunderbird began releasing updates more quickly, similar to Firefox. By the end of 2011, it had reached version 9.0.

In 2012, Mozilla announced that they would focus less on adding new features to Thunderbird and instead rely more on community contributions. However, in 2014, volunteers decided they needed more full-time help to improve Thunderbird.

In 2015, Mozilla announced that Thunderbird would become more independent from Firefox, allowing it to grow in its own way.

In 2017, Thunderbird started using a new design inspired by Firefox. Over the next few years, Thunderbird added new features like better security, support for newer computers, and tools for managing contacts.

In 2020, Thunderbird began operating under a new company called MZLA Technologies Corporation.

Thunderbird 91 added many improvements, including better setup for new users, support for newer computers, and built-in tools for handling documents.

In 2022, the Thunderbird team began working on a mobile version of Thunderbird for phones, taking over development of an existing app called K-9 Mail. By November 2024, Thunderbird Mobile was available for download, and in December 2024, it became the default email app on some Android devices.

Releases

Thunderbird has three stages of testing before a final release: Beta, Earlybird, and Daily. These stages match Firefox's testing stages. For example, both Firefox 7 and Thunderbird 7 were released on the same day and used the same technology.

Thunderbird Pro

On April 4, 2025, the Thunderbird team shared news about future paid services called "Thunderbird Pro". These services will be based on the internet and aim to offer privacy while competing with platforms like Google Workspace and Microsoft 365. The core Thunderbird email app will stay free, and the Pro services will be an optional add-on. These new services will include features that need internet servers to work.

The plan is to charge for these services to cover costs, with hopes to offer a basic free option later. All parts of Thunderbird Pro will be open source and use open standards so users can switch services easily.

The services planned for Thunderbird Pro include:

• Thundermail: An email service with calendar and contact hosting, aiming to be ad-free and respectful of privacy. It will offer email addresses at thundermail.com or tb.pro, plus support for custom domains. Thundermail will use the open-source software stack Stalwart.
• Thunderbird Appointment: A tool for sharing links so others can book meetings on your calendar. As of June 9, 2025, this service is in a testing phase.
• Thunderbird Send: A service for sharing large files with strong privacy protection. It is described as a continuation of Firefox Send. The source code for Send is available on GitHub.
• Thunderbird Assist: An experimental, optional feature to add smart capabilities. Developed with Flower AI, it aims to use local processing on devices when possible and private internet processing when needed.

At the time of the announcement, Appointment was in testing, Send was in an early development stage, and people could join a waitlist for Thundermail testing.