Mozilla Thunderbird is a

free and open-source Free and open-source software (FOSS) is a term used to refer to groups of software consisting of both free software and open-source software where anyone is freely licensed to use, copy, study, and change the software in any way, and the source ...

cross-platform In computing, cross-platform software (also called multi-platform software, platform-agnostic software, or platform-independent software) is computer software that is designed to work in several computing platforms. Some cross-platform software ...

email client An email client, email reader or, more formally, message user agent (MUA) or mail user agent is a computer program used to access and manage a user's email. A web application which provides message management, composition, and reception functio ...

, personal information manager,

news client A newsreader is an application program that reads articles on Usenet distributed throughout newsgroups. Newsreaders act as clients which connect to a news server, via the Network News Transfer Protocol (NNTP), to download articles and post new a ...

, RSS and chat client developed by the

Mozilla Foundation The Mozilla Foundation (stylized as moz://a) is an American non-profit organization that exists to support and collectively lead the open source Mozilla project. Founded in July 2003, the organization sets the policies that govern development, ...

and operated by subsidiary MZLA Technologies Corporation. The project strategy was originally modeled after that of Mozilla's

Firefox Mozilla Firefox, or simply Firefox, is a free and open-source web browser developed by the Mozilla Foundation and its subsidiary, the Mozilla Corporation. It uses the Gecko rendering engine to display web pages, which implements current ...

web browser A web browser is application software for accessing websites. When a user requests a web page from a particular website, the browser retrieves its files from a web server and then displays the page on the user's screen. Browsers are used o ...

Features

Thunderbird is an email, newsgroup, news feed, and chat (

XMPP Extensible Messaging and Presence Protocol (XMPP, originally named Jabber) is an open communication protocol designed for instant messaging (IM), presence information, and contact list maintenance. Based on XML (Extensible Markup Language), i ...

/ IRC) client with personal information manager (PIM) functionality, inbuilt since version 78.0 and previously available from the

Lightning Lightning is a naturally occurring electrostatic discharge during which two electrically charged regions, both in the atmosphere or with one on the ground, temporarily neutralize themselves, causing the instantaneous release of an average ...

calendar extension. Additional features are available from

extensions Extension, extend or extended may refer to: Mathematics Logic or set theory * Axiom of extensionality * Extensible cardinal * Extension (model theory) * Extension (predicate logic), the set of tuples of values that satisfy the predicate * Ex ...

Message management

Thunderbird manages multiple email, newsgroup, and news feed accounts and supports multiple identities within accounts. Features such as quick search, saved search folders ("virtual folders"), advanced message

filtering Filter, filtering or filters may refer to: Science and technology Computing * Filter (higher-order function), in functional programming * Filter (software), a computer program to process a data stream * Filter (video), a software component tha ...

, message grouping, and tags help manage and find messages. On

Linux Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, whi ...

-based systems, system mail ( movemail) accounts were supported until version 91.0. Thunderbird provides basic support for system-specific new email notifications and can be extended with advanced notification support using an add-on.

Junk filtering

Thunderbird incorporates a

Bayesian Thomas Bayes (/beɪz/; c. 1701 – 1761) was an English statistician, philosopher, and Presbyterian minister. Bayesian () refers either to a range of concepts and approaches that relate to statistical methods based on Bayes' theorem, or a followe ...

spam Spam may refer to: * Spam (food), a canned pork meat product * Spamming, unsolicited or undesired electronic messages ** Email spam, unsolicited, undesired, or illegal email messages ** Messaging spam, spam targeting users of instant messaging ...

filter, a whitelist based on the included address book, and can also understand classifications by server-based filters such as

SpamAssassin Apache SpamAssassin is a computer program used for e-mail spam filtering. It uses a variety of spam-detection techniques, including DNS and fuzzy checksum techniques, Bayesian filtering, external programs, blacklists and online databases. It i ...

Extensions and themes

Extensions allow the addition of features through the installation of

XPInstall XPInstall (Cross-Platform Install) is a technology used by the Mozilla Application Suite, SeaMonkey, Mozilla Firefox, Mozilla Thunderbird and other XUL-based applications for installing Mozilla extensions that add functionality to the main applic ...

modules (known as "XPI" or "zippy" installation) via the add-ons website that also features an update functionality to update the extensions. Thunderbird supports a variety of

themes Theme or themes may refer to: * Theme (arts), the unifying subject or idea of the type of visual work * Theme (Byzantine district), an administrative district in the Byzantine Empire governed by a Strategos * Theme (computing), a custom graphical ...

for changing its overall look and feel. These packages of

CSS Cascading Style Sheets (CSS) is a style sheet language used for describing the presentation of a document written in a markup language such as HTML or XML (including XML dialects such as SVG, MathML or XHTML). CSS is a cornerstone technolo ...

and

image An image is a visual representation of something. It can be two-dimensional, three-dimensional, or somehow otherwise feed into the visual system to convey information. An image can be an artifact, such as a photograph or other two-dimensio ...

files can be downloaded via the add-ons website at Mozilla Add-ons.

Standards support

Thunderbird follows industry standards for email: *

POP Pop or POP may refer to: Arts, entertainment, and media Music * Pop music, a musical genre Artists * POP, a Japanese idol group now known as Gang Parade * Pop!, a UK pop group * Pop! featuring Angie Hart, an Australian band Albums * ''Pop'' ( ...

. Basic email retrieval protocol. *

IMAP In computing, the Internet Message Access Protocol (IMAP) is an Internet standard protocol used by email clients to retrieve email messages from a mail server over a TCP/IP connection. IMAP is defined by . IMAP was designed with the goal of per ...

. Thunderbird has implemented many of the capabilities in IMAP, in addition to adding their own extensions and the de facto standards by Google and Apple. *

LDAP The Lightweight Directory Access Protocol (LDAP ) is an open, vendor-neutral, industry standard application protocol for accessing and maintaining distributed directory information services over an Internet Protocol (IP) network. Directory servi ...

address auto-completion. * S/MIME: Inbuilt support for email encryption and signing using X.509 keys provided by a centralised certificate authority. *

OpenPGP Pretty Good Privacy (PGP) is an encryption program that provides cryptographic privacy and authentication for data communication. PGP is used for signing, encrypting, and decrypting texts, e-mails, files, directories, and whole disk partiti ...

: Inbuilt support for email encryption and signing since version 78.2.1, while older versions used extensions such as

Enigmail Enigmail is a data encryption and decryption extension for Mozilla Thunderbird and the Postbox that provides OpenPGP public key e-mail encryption and signing. Enigmail works under Microsoft Windows, Unix-like, and Mac OS X operating systems. En ...

. For web feeds (''e.g.''

news aggregator In computing, a news aggregator, also termed a feed aggregator, feed reader, news reader, RSS reader or simply an aggregator, is client software or a web application that aggregates syndicated web content such as online newspapers, blogs, ...

s), it supports

Atom Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons. Every solid, liquid, gas, a ...

and RSS. For chat, it supports the IRC and

protocol. For newsfeeds, it uses

NNTP The Network News Transfer Protocol (NNTP) is an application protocol used for transporting Usenet news articles (''netnews'') between news servers, and for reading/posting articles by the end user client applications. Brian Kantor of the Univers ...

and supports NNTPS.

File formats supported

Thunderbird provides mailbox format support using plugins, but this feature is not yet enabled due to related work in progress. The mailbox formats supported are: *

mbox Mbox is a generic term for a family of related file formats used for holding collections of email messages. It was first implemented in Fifth Edition Unix. All messages in an mbox mailbox are concatenated and stored as plain text in a single f ...

– Unix mailbox format (one file holding many emails) * maildir – known as maildir-lite (one file per email). "there are still many bugs", so this is disabled by default. Thunderbird also uses Mork and (since version 3) MozStorage (which is based on

SQLite SQLite (, ) is a database engine written in the C programming language. It is not a standalone app; rather, it is a library that software developers embed in their apps. As such, it belongs to the family of embedded databases. It is the mo ...

) for its internal database. Mork was due to be replaced with MozStorage in Thunderbird 3.0, but the 8.0 release still uses the Mork file format.

Big file linking

Since version 38, Thunderbird has integrated support for automatic linking of large files instead of attaching them directly to the mail message.

HTML formatting and code insertion

Thunderbird provides a

wysiwyg In computing, WYSIWYG ( ), an acronym for What You See Is What You Get, is a system in which editing software allows content to be edited in a form that resembles its appearance when printed or displayed as a finished product, such as a printed d ...

editor for composing messages formatted with HTML (default). The delivery format auto-detect feature will send unformatted messages as plain text (controlled by a user preference). Certain special formatting like subscript, superscript and

strikethrough Strikethrough is a typographical presentation of words with a horizontal line through their center, resulting in . Contrary to censored or sanitized (redacted) texts, the words remain readable. This presentation signifies one of two meanings. I ...

is available from the Format menu. The Insert > HTML menu provides the ability to edit the

HTML The HyperText Markup Language or HTML is the standard markup language for documents designed to be displayed in a web browser. It can be assisted by technologies such as Cascading Style Sheets (CSS) and scripting languages such as JavaS ...

source code of the message. There is basic support for HTML template messages, which are stored in a dedicated templates folder for each account.

Markdown Markdown is a lightweight markup language for creating formatted text using a plain-text editor. John Gruber and Aaron Swartz created Markdown in 2004 as a markup language that is appealing to human readers in its source code form. Markdown i ...

support is provided through th
Markdown here Revival
add-on.

Limitations and known issues

As with any software, there may be limitations to the number and sizes of files and objects represented. For example,

POP3 In computing, the Post Office Protocol (POP) is an application-layer Internet standard protocol used by e-mail clients to retrieve e-mail from a mail server. POP version 3 (POP3) is the version in common use, and along with IMAP the most common ...

folders are subject to filesystem design limitations, such as maximum file sizes on filesystems that do not have

large-file support Large-file support (LFS) is the term frequently applied to the ability to create files larger than either 2 or 4 GiB on 32-bit filesystems. Details Traditionally, many operating systems and their underlying file system implementations use ...

, as well as possible limitations of

long filename Long filename (LFN) support is Microsoft's backward-compatible extension of the 8.3 filename (short filename) naming scheme used in DOS. Long filenames can be more descriptive, including longer filename extensions such as .jpeg, .tiff, .html, ...

s, and other issues.

Cross-platform support

Thunderbird runs on a variety of platforms. Releases available on the primary distribution site support the following operating systems: *

Windows Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for se ...

macOS macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac computers. Within the market of desktop and la ...

Unofficial ports are available for: *

FreeBSD FreeBSD is a free and open-source Unix-like operating system descended from the Berkeley Software Distribution (BSD), which was based on Research Unix. The first version of FreeBSD was released in 1993. In 2005, FreeBSD was the most popular ...

OpenBSD OpenBSD is a security-focused, free and open-source, Unix-like operating system based on the Berkeley Software Distribution (BSD). Theo de Raadt created OpenBSD in 1995 by forking NetBSD 1.0. According to the website, the OpenBSD project e ...

Ports for older versions available for

OS/2 OS/2 (Operating System/2) is a series of computer operating systems, initially created by Microsoft and IBM under the leadership of IBM software designer Ed Iacobucci. As a result of a feud between the two companies over how to position OS/2 r ...

(including

ArcaOS ArcaOS is an operating system based on OS/2, developed and marketed by Arca Noae, LLC under license from IBM. It was codenamed Blue Lion during its development. It builds on OS/2 Warp 4.52 by adding support for new hardware, fixing defects and li ...

and eComStation). The source code is freely available and can be compiled to be run on a variety of other architectures and operating systems.

Android version

In June 2022, the Thunderbird project announced that it would be collaborating with email client K-9 for Android to build a Thunderbird version for Android. To this end, K-9 lead developer Christian Ketterer joined the Thunderbird team in 2022. The plan was to transform K-9 Mail into Thunderbird on Android, including the respective name change and adoption of the Thunderbird branding. As soon as K-9 Mail had been brought into alignment with Thunderbird’s feature set and visual appearance, this changeover would take place, according to Thunderbird's Jason Evangelho.

Internationalization and localization

With contributors all over the world, Thunderbird has been translated into more than 65 languages, although email addresses are currently limited to ASCII local parts. Thunderbird does not yet support SMTPUTF8 (RFC 6531) or

Email Address Internationalization An email address identifies an email box to which messages are delivered. While early messaging systems used a variety of formats for addressing, today, email addresses follow a set of specific rules originally standardized by the Internet Engine ...

Security

Thunderbird provides security features such as

TLS/SSL Transport Layer Security (TLS) is a cryptographic protocol designed to provide communications security over a computer network. The protocol is widely used in applications such as email, instant messaging, and voice over IP, but its use in secur ...

connections to

and

SMTP The Simple Mail Transfer Protocol (SMTP) is an Internet standard communication protocol for electronic mail transmission. Mail servers and other message transfer agents use SMTP to send and receive mail messages. User-level email clients ty ...

servers. It also offers inbuilt support for secure email with digital signing and message

encryption In cryptography, encryption is the process of encoding information. This process converts the original representation of the information, known as plaintext, into an alternative form known as ciphertext. Ideally, only authorized parties can d ...

through

(using public and private

keys Key or The Key may refer to: Common meanings * Key (cryptography), a piece of information that controls the operation of a cryptography algorithm * Key (lock), device used to control access to places or facilities restricted by a lock * Key (m ...

) or S/MIME (using certificates). Any of these security features can take advantage of smartcards with the installation of additional extensions. Other security features may be added through extensions. Up to version 68, the

extension was required for

support (now inbuilt). Optional security protections also include disabling loading of remote images within messages, enabling only specific media types (sanitizer), and disabling

JavaScript JavaScript (), often abbreviated as JS, is a programming language that is one of the core technologies of the World Wide Web, alongside HTML and CSS. As of 2022, 98% of websites use JavaScript on the client side for webpage behavior, of ...

. The French military uses Thunderbird and contributes to its security features, which are claimed to match the requirements for

NATO The North Atlantic Treaty Organization (NATO, ; french: Organisation du traité de l'Atlantique nord, ), also called the North Atlantic Alliance, is an intergovernmental military alliance between 30 member states – 28 European and two N ...

's closed messaging system.

History

Originally launched as ''Minotaur'' shortly after '' Phoenix'' (the original name for Mozilla Firefox), the project failed to gain momentum. With the success of Firefox, however, demand increased for a mail client to go with it, and the work on Minotaur was revived under the new name of Thunderbird, and migrated to the new toolkit developed by the Firefox team. On December 7, 2004, version 1.0 was released, and received more than 500,000 downloads in its first three days of release, and 1,000,000 in ten days. Significant work on Thunderbird restarted with the announcement that from version 1.5 onward the main Mozilla suite would be designed around separate applications using this new toolkit. This contrasts with the previous all-in-one approach, allowing users to mix and match the Mozilla applications with alternatives. The original Mozilla Suite continues to be developed as SeaMonkey. On December 23, 2004, Project Lightning was announced which tightly integrated

calendar A calendar is a system of organizing days. This is done by giving names to periods of time, typically days, weeks, months and years. A date is the designation of a single and specific day within such a system. A calendar is also a phy ...

functionality (scheduling, tasks, etc.) into Thunderbird. Lightning supports the full range of calendar mechanisms and protocols supported by the Mozilla Calendar infrastructure, just as with modern (post-0.2) Sunbird. On October 11, 2006,

Qualcomm Qualcomm () is an American multinational corporation headquartered in San Diego, California, and incorporated in Delaware. It creates semiconductors, software, and services related to wireless technology. It owns patents critical to the 5G, ...

and the Mozilla Foundation announced that "future versions of

Eudora Eudora may refer to: Places * Eudora, Arkansas, a city * Eudora, Kansas, a city * Eudora Township, Douglas County, Kansas * Eudora, Mississippi, an unincorporated community * Eudora, Missouri, an unincorporated community Other * 217 Eudora, an as ...

will be based upon the same technology platform as the open source Mozilla Thunderbird email program." The project was code-named

Penelope Penelope ( ; Ancient Greek: Πηνελόπεια, ''Pēnelópeia'', or el, Πηνελόπη, ''Pēnelópē'') is a character in Homer's ''Odyssey.'' She was the queen of Ithaca and was the daughter of Spartan king Icarius and naiad Periboea. Pe ...

. In late 2006,

Debian Debian (), also known as Debian GNU/Linux, is a Linux distribution composed of free and open-source software, developed by the community-supported Debian Project, which was established by Ian Murdock on August 16, 1993. The first version of De ...

rebranded Thunderbird as Icedove due to trademark and copyright reasons. This was the second product to be rebranded. On July 26, 2007, the Mozilla Foundation announced that Thunderbird would be developed by an independent organization, because the

Mozilla Corporation The Mozilla Corporation (stylized as moz://a) is a wholly owned subsidiary of the Mozilla Foundation that coordinates and integrates the development of Internet-related applications such as the Firefox web browser, by a global community of ope ...

(a subsidiary of the foundation) was focusing on Mozilla Firefox development. On September 17, 2007, the Mozilla Foundation announced the funding of a new internet communications initiative with David Ascher of ActiveState. The purpose of this initiative was "to develop Internet communications software based on the Thunderbird product, code, and brand". On February 19, 2008, Mozilla Messaging started operations as a subsidiary of the Mozilla Foundation responsible for the development of email and similar communications. Its initial focus was on the then upcoming version of Thunderbird 3. Alpha Preview releases of Thunderbird 3 were codenamed "Shredder". On April 4, 2011, Mozilla Messaging was merged into the Mozilla Labs group of the Mozilla Foundation. On July 6, 2012, a confidential memo from Jb Piacentino, the Thunderbird Managing Director at Mozilla, was leaked and published to

TechCrunch TechCrunch is an American online newspaper An online newspaper (or electronic news or electronic news publication) is the online version of a newspaper, either as a stand-alone publication or as the online version of a printed periodical. Goi ...

. The memo indicated that Mozilla would be moving some of the team off the project and further development of new features would be left up to the community. The memo was slated for release on July 9, 2012. A subsequent article by the Executive Chair of Mozilla,

Mitchell Baker Winifred Mitchell Baker (born 1957) is the Executive Chairwoman and CEO of the Mozilla Foundation and of Mozilla Corporation, a subsidiary of the Mozilla Foundation that coordinates development of the open source Mozilla Internet applicati ...

, stated Mozilla's decision to make a transition of Thunderbird to a new release and governance model. On July 6, 2012, Mozilla announced the company was dropping the priority of Thunderbird development because the continuous effort to extend Thunderbird's feature set was mostly fruitless. The new development model shifted to Mozilla offering only "Extended Support Releases", which deliver security and maintenance updates, while allowing the community to take over the development of new features. On November 25, 2014, Kent James of the volunteer-led Thunderbird Council announced on the Thunderbird blog that active contributors to Thunderbird gathered at the Mozilla office in Toronto and discussed the future of the application. They decided that more staff were required working full-time on Thunderbird so that the Thunderbird Team could release a stable and reliable product and make progress on features that had been frequently requested by the community. On December 1, 2015, Mozilla Executive Chair

announced in a company-wide memo that Thunderbird development needed to be uncoupled from Firefox. She referred to Thunderbird developers spending large efforts responding to changes to Mozilla technologies, while Firefox was paying a tax to support Thunderbird development. She also said that she does not believe Thunderbird has the potential for "industry-wide impact" that Firefox does. Mozilla remained interested in having a role in Thunderbird, but sought more assistance to help with development. Therefore, at the same time, it was announced that Mozilla Foundation would provide at least a temporary legal and financial home for the Thunderbird project. On May 9, 2017, Philipp Kewisch announced that the Mozilla Foundation would continue to serve as the legal and fiscal home for the Thunderbird project, but that Thunderbird would migrate off Mozilla Corporation infrastructure, separating the operational aspects of the project. Mozilla brought Thunderbird back in-house in an announcement on May 9, 2017, and continued to support its development. The Thunderbird development team expanded by adding several new members and overhauled security and the user interface. The interim/beta versions Thunderbird 57 and 58, released in late 2017, began to make changes influenced by

Firefox Quantum Firefox was created by Dave Hyatt and Blake Ross as an experimental branch of the Mozilla browser, first released as Firefox 1.0 on November 9, 2004. Starting with version 5.0, a rapid release cycle was put into effect, resulting in a new ...

, including a new "Photon" user interface. Despite the removal in Firefox Quantum of support for

XUL XUL ( ), which stands for XML User Interface Language, is a user interface markup language developed by Mozilla. XUL is an XML dialect for writing graphical user interfaces, enabling developers to write user interface elements in a manner sim ...

-based legacy add-ons in favor of WebExtensions, the stable/ESR release of Thunderbird 60 in mid-2018 continued to support them, although most would require updates, and it did not support WebExtensions except for Themes. In 2018, work was underway for planned support in Thunderbird 63 of WebExtensions and to continue to "somewhat" support legacy addons, according to Mozilla. With the release of Thunderbird 68 in August 2019 it now only supports WebExtension addons. Legacy Addons can still be used if a special "legacy mode" is enabled, but even for this, the legacy Addon has to be converted. Alongside the transition,

support was integrated directly into Thunderbird as a standard feature, seeking to supplant the

extension. Mainly for licensing reasons, this is no longer based on GnuPG, but on the RNP library, which has more liberal licensing terms. On January 28, 2020, the Mozilla Foundation announced that the project would henceforth be operating from a new wholly owned subsidiary, MZLA Technologies Corporation, in order to explore offering products and services that were not previously possible and to collect revenue through partnerships and non-charitable donations. As of version 78.7.1, Thunderbird will no longer allow installation of addons that use Legacy WebExtensions. Only MailExtensions are now compatible with Thunderbird. MailExtensions are WebExtensions but with "some added features specific to Thunderbird". Thunderbird 91 features various UI improvements (including a new account setup workflow),

Apple silicon Apple silicon is a series of system on a chip (SoC) and system in a package (SiP) processors designed by Apple Inc., mainly using the ARM architecture. It is the basis of most new Mac computers as well as iPhone, iPad, iPod Touch, Apple TV, ...

support,

CardDAV vCard Extensions to WebDAV (CardDAV) is an address book client/server protocol designed to allow users to access and share contact data on a server. The CardDAV protocol was developed by the IETF and was published as in August 2011. CardDAV is ...

address book support, built-in import and export tools for Thunderbird profiles, the PDF.js

PDF Portable Document Format (PDF), standardized as ISO 32000, is a file format developed by Adobe in 1992 to present documents, including text formatting and images, in a manner independent of application software, hardware, and operating systems. ...

viewer, and the ability to encrypt emails to BCC recipients. On June 13, 2022, it was announced that the Mozilla Thunderbird team would take over development of the Android email client app K-9 Mail, with plans for it to eventually become a mobile version of Thunderbird with synchronisation support.

Releases

Thunderbird development releases occur in three stages, called Beta, Earlybird, and Daily, which correspond to Firefox's Beta, Aurora, and Nightly stages. The release dates and

Gecko Geckos are small, mostly carnivorous lizards that have a wide distribution, found on every continent except Antarctica. Belonging to the infraorder Gekkota, geckos are found in warm climates throughout the world. They range from . Geckos a ...

versions are exactly the same as Firefox; for example, Firefox 7 and Thunderbird 7 were both released on September 27, 2011, and were both based on Gecko 7.0.

References

External links

* {{Authority control 2003 software Cross-platform free software Email client software for Linux Free email software Free multilingual software Free software programmed in C++ Free Usenet clients Gecko-based software macOS email clients News aggregator software OS/2 software Portable software Software that uses SQLite Software that uses XUL Software using the Mozilla license Unix Internet software Windows email clients