What is Thunderbird?
Thunderbird is an email client that connects to accounts from almost any provider through the standard IMAP, POP3 and SMTP protocols, and since version 145 in late 2025 it has also supported Microsoft Exchange natively. Several accounts can be managed side by side, with unified folders that combine inboxes, message filters, tags, saved searches and a tabbed interface for keeping messages, calendars and address books open at once.
Beyond email, Thunderbird includes a calendar and task list, an address book, a reader for RSS and Atom feeds and Usenet newsgroups, and chat for networks such as Matrix, XMPP and IRC. Built-in OpenPGP support, added in 2020, lets users send end-to-end encrypted email without installing a separate plugin, and add-ons extend the app further. A redesign code-named Supernova, released with version 115 in 2023, modernized its interface.
MZLA Technologies, a wholly owned subsidiary of the Mozilla Foundation, develops Thunderbird with volunteer contributors, and the project says its work is funded by individual donations. In 2025 monthly releases became the default for the desktop app, alongside a yearly Extended Support Release. An Android app based on the open-source K-9 Mail client launched in 2024, and an iOS version was being tested through Apple’s TestFlight in 2026. MZLA also began inviting beta users in May 2026 to Thundermail, a paid email hosting service that works with any standard email client.
Key features of Thunderbird
- 01
Multiple account support
Users can manage many email accounts from different providers in one app over IMAP, POP3 and SMTP or native Microsoft Exchange support, with unified folders that combine their inboxes.
- 02
Calendar and tasks
A built-in calendar handles events, meeting invitations, reminders and to-do lists, and it can connect to CalDAV and ICS calendars hosted by other services.
- 03
OpenPGP and S/MIME encryption
Thunderbird can sign and encrypt messages with OpenPGP keys or S/MIME certificates, giving end-to-end encryption to correspondents who use compatible email software.
- 04
Filters, tags and search
Message filters sort, flag and move incoming mail automatically, while tags, saved search folders and full-text search help users organize and find messages in large mailboxes.
- 05
Feeds, newsgroups and chat
The same app can follow RSS and Atom feeds, read Usenet newsgroups and connect to chat networks including Matrix, XMPP and IRC.
- 06
Add-ons and themes
Extensions from addons.thunderbird.net add capabilities such as mail merge and delayed sending, and themes change the look of the application.
- 07
Thunderbird for Android
The Android app, developed from the K-9 Mail client, supports multiple accounts, a unified inbox and OpenPGP encryption, bringing Thunderbird’s email tools to phones and tablets.
Who uses Thunderbird?
- Home users with email accounts at several providers read and send all of their mail from one desktop application.
- Privacy-minded users and journalists send OpenPGP-encrypted email and keep local copies of their messages instead of relying only on webmail.
- Small businesses, schools and nonprofits deploy Thunderbird as a free desktop client for staff email, calendars and address books.
- Linux users often rely on Thunderbird because distributions such as Ubuntu include it as the default email client.
History of Thunderbird
Thunderbird started inside the Mozilla project as Minotaur, a standalone mail program meant to do for email what Phoenix, later Firefox, was doing for browsing. Renamed Thunderbird, version 0.1 appeared on July 28, 2003, and version 1.0 followed in December 2004. From 2008 to 2011 a separate subsidiary called Mozilla Messaging developed it before the work was folded back into Mozilla.
In 2012 Mozilla said it would stop prioritizing Thunderbird and hand more responsibility to its community. The project gained an elected Thunderbird Council, confirmed the Mozilla Foundation as its legal and financial home in 2017, and in January 2020 moved into MZLA Technologies Corporation, a subsidiary created to run it. Donations have since paid for a larger staff, which brought the K-9 Mail project on board in 2022, shipped the Supernova redesign in 2023 and the Android app in 2024, added native Exchange support in 2025 and began testing Thundermail in 2026.
- 2003
The Mozilla project releases Thunderbird 0.1, a standalone email client, on July 28.
- 2004
Thunderbird 1.0 is released in December, a month after Firefox 1.0.
- 2012
Mozilla stops prioritizing Thunderbird and gives its community more responsibility for development.
- 2020
MZLA Technologies Corporation is formed to develop Thunderbird, and OpenPGP support is built in.
- 2023
Thunderbird 115, code-named Supernova, introduces a redesigned interface.
- 2024
Thunderbird for Android, based on the K-9 Mail client, is released.
- 2025
Monthly releases become the default, and native Microsoft Exchange support arrives in version 145.
- 2026
MZLA begins inviting beta testers to Thundermail, its email hosting service, in May.
Thunderbird pricing
Pricing modelFree and open source
The desktop and Android apps are free and funded by user donations; Thundermail, a separate paid email hosting service, was in an invite-only beta in 2026.
Prices change often. Check the official Thunderbird website for current plans.
Thunderbird alternatives
Well-known alternativesMicrosoft Outlook, Apple Mail, eM Client, Mailspring and Evolution
Thunderbird: frequently asked questions
Who makes Thunderbird?
Thunderbird is made by MZLA Technologies Corporation, a wholly owned subsidiary of the non-profit Mozilla Foundation, with help from volunteer contributors. MZLA is a sister organization to Mozilla Corporation, which develops Firefox, and Ryan Sipes leads it as CEO.
What is Thunderbird used for?
Thunderbird is used to read, write and organize email from one or more accounts in a single app. It also manages calendars, tasks and contacts, reads RSS feeds and newsgroups, connects to chat networks and can send encrypted email using OpenPGP or S/MIME.
Is Thunderbird free?
Yes. Thunderbird’s desktop and Android apps are free and open source under the Mozilla Public License 2.0, and development is funded by user donations. The team separately offers Thundermail, a paid email hosting service that was in an invite-only beta in 2026.
When was Thunderbird released?
Thunderbird 0.1 was released on July 28, 2003, as a standalone email client from the Mozilla project, and Thunderbird 1.0 followed in December 2004. The Android version was released in 2024.
Is Thunderbird available for iPhone?
Not yet as a finished app. Thunderbird is available for Windows, macOS, Linux and Android, and in 2026 its developers were building an iOS version that testers could try through Apple’s TestFlight program, with no public App Store release date announced.
What is Thundermail?
Thundermail is an email hosting service from the team behind Thunderbird that also includes the Appointment scheduling tool and the Send file-sharing service. First announced in 2025 as part of a subscription bundle called Thunderbird Pro, it began inviting early beta users in May 2026 and works with any standard email client.
Sources
- Thunderbird thunderbird.net
- Thunderbird 2025 Review: Building Stronger for the Future blog.thunderbird.net
- Thundermail June 2026 update blog.thunderbird.net
- Mozilla Thunderbird, Wikipedia en.wikipedia.org
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