HowItWorks:Thunderbird - Revision history

Rongzhou: /* Components and interactions */

2026-09-01T21:31:11Z

Components and interactions

← Older revision		Revision as of 21:31, 1 September 2026
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	note right of MAILNEWS		note right of MAILNEWS
	mailnews/ is the shared Mail and		mailnews/ is the shared Mail and
	Newsgroups backend, also used by		Newsgroups backend. It is also
	SeaMonkey.		used by SeaMonkey.
	end note		end note
	note right of EXT		note right of EXT
	~~Add~~-ons ~~are optional: the core~~		Optional add-ons consumes
	~~application does not depend on~~		dedicated MailExtension APIs
	~~them. They consume~~ MailExtension		provided by the application layer.
	~~APIs~~ provided by the application,
	~~run as JavaScript on SpiderMonkey,~~
	~~and render their UI through Gecko~~.
	end note		end note
	note right of NECKO		note right of NECKO
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	Thunderbird's UI is rendered by		Thunderbird's UI is rendered by
	the same engine that renders		the same engine that renders
	web pages in Firefox.		web pages in Firefox: Gecko
	end note		end note

Rongzhou: /* Source code organization */

2026-09-01T21:26:26Z

Source code organization

← Older revision		Revision as of 21:26, 1 September 2026
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	The profile directory holds the mail folders on disk and several SQLite databases: the address book back end keeps its books in SQLite (abook.sqlite),<ref>{{#cite:Q1510}}</ref> the calendar component stores events in local.sqlite,<ref>{{#cite:Q1512}}</ref> and the global message database (global-messages-db.sqlite) powers message indexing and search.<ref>{{#cite:Q1513}}</ref>		The profile directory holds the mail folders on disk and several SQLite databases: the address book back end keeps its books in SQLite (abook.sqlite),<ref>{{#cite:Q1510}}</ref> the calendar component stores events in local.sqlite,<ref>{{#cite:Q1512}}</ref> and the global message database (global-messages-db.sqlite) powers message indexing and search.<ref>{{#cite:Q1513}}</ref>

	=== Source code ~~organization~~ ===		=== Source code organisation ===

	Thunderbird's source code repository is split into multiple sub-directories by functionality:<ref>{{#cite:Q1494}}</ref>		Thunderbird's source code repository is split into multiple sub-directories by functionality:<ref>{{#cite:Q1494}}</ref>

RonzzWikiCowriterAI: Redraw components diagram per review: route all external connections through Necko; extensions are optional consumers (reverse arrow), run on SpiderMonkey and render via Gecko; AI-assisted (RonzzWikiCowriter) (via update-page on MediaWiki MCP Server)

2026-09-01T21:24:46Z

Redraw components diagram per review: route all external connections through Necko; extensions are optional consumers (reverse arrow), run on SpiderMonkey and render via Gecko; AI-assisted (RonzzWikiCowriter) (via update-page on MediaWiki MCP Server)

← Older revision		Revision as of 21:24, 1 September 2026
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	' ============= APPLICATION LAYER =============		' ============= APPLICATION LAYER =============
	node "Application layer" {		node "Application layer" {
	component "mail/ modules & components\n(account setup, cloudfile,\npreferences, ~~extensions~~)" as APPMOD		component "mail/ modules & components\n(account setup, cloudfile,\npreferences, MailExtension APIs)" as APPMOD
	component "Address book backend\n(mailnews/addrbook)" as ABBACK		component "Address book backend\n(mailnews/addrbook)" as ABBACK
			}

			' ============= ADD-ONS (optional) =============
			node "Add-ons" {
	component "MailExtensions\n(WebExtensions + Experiments)" as EXT		component "MailExtensions\n(WebExtensions + Experiments)" as EXT
	}		}
Line 121:		Line 125:
	CALUI --> CALBACK : events & tasks		CALUI --> CALBACK : events & tasks
	CHATUI --> CHATPROTO : conversations		CHATUI --> CHATPROTO : conversations
	APPMOD --> EXT : ~~extension API~~		EXT --> APPMOD : use MailExtension APIs
			EXT --> SM : run JS\n(background & content scripts)
			EXT --> GECKO : render add-on UI
	APPMOD --> GECKO : render UI\n(HTML / XUL)		APPMOD --> GECKO : render UI\n(HTML / XUL)
	APPMOD --> SM : run JS modules		APPMOD --> SM : run JS modules
Line 129:		Line 135:
	MAILNEWS --> MBOX : read / write messages		MAILNEWS --> MBOX : read / write messages
	CALBACK --> SQLITE : store events & tasks		CALBACK --> SQLITE : store events & tasks
	MAILNEWS --> NECKO : ~~protocol connections~~		MAILNEWS --> NECKO : IMAP / POP3 / SMTP / NNTP
	CALBACK --> NECKO : CalDAV / WebDAV		CALBACK --> NECKO : CalDAV / WebDAV
	CHATPROTO --> NECKO : ~~chat protocols~~		CHATPROTO --> NECKO : IRC / XMPP / Matrix
	~~MAILNEWS~~ --> MAILSVR : ~~IMAP / POP3 / SMTP~~		APPMOD --> NECKO : autoconfig & ISPDB lookups
	~~CALBACK~~ --> CALDAVSVR : CalDAV/WebDAV		NECKO --> MAILSVR : sockets & TLS
	~~CHATPROTO~~ --> CHATSVR : ~~chat servers~~		NECKO --> CALDAVSVR : HTTP (CalDAV / WebDAV)
	~~APPMOD~~ --> ISPDB : ~~autoconfig~~ lookup		NECKO --> CHATSVR : sockets / HTTP / WebSocket
	~~EXT~~ --> AMO : install / update		NECKO --> ISPDB : HTTP lookup
			NECKO --> AMO : add-on install / update\n(HTTP downloads)

	note right of SQLITE		note right of SQLITE
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	end note		end note
	note right of EXT		note right of EXT
	Add-ons ~~use stable WebExtension~~		Add-ons are optional: the core
	APIs~~; "Experiment" APIs can reach~~		application does not depend on
	~~into internal Thunderbird APIs~~.		them. They consume MailExtension
			APIs provided by the application,
			run as JavaScript on SpiderMonkey,
			and render their UI through Gecko.
			end note
			note right of NECKO
			Necko is the platform networking
			library: every connection to an
			external server (mail, calendar,
			chat, autoconfig, add-on
			downloads) goes through it.
	end note		end note
	note right of GECKO		note right of GECKO
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	@enduml		@enduml
	</uml>		</uml>

			Every connection to an outside server flows through '''Necko''', the Mozilla platform's networking library: the mail protocol implementations open their sockets through Necko's socket transport service, and HTTP-based traffic (CalDAV, autoconfiguration, add-on downloads) uses its HTTP channels.<ref>{{#cite:Q1516}}</ref>

	The profile directory holds the mail folders on disk and several SQLite databases: the address book back end keeps its books in SQLite (abook.sqlite),<ref>{{#cite:Q1510}}</ref> the calendar component stores events in local.sqlite,<ref>{{#cite:Q1512}}</ref> and the global message database (global-messages-db.sqlite) powers message indexing and search.<ref>{{#cite:Q1513}}</ref>		The profile directory holds the mail folders on disk and several SQLite databases: the address book back end keeps its books in SQLite (abook.sqlite),<ref>{{#cite:Q1510}}</ref> the calendar component stores events in local.sqlite,<ref>{{#cite:Q1512}}</ref> and the global message database (global-messages-db.sqlite) powers message indexing and search.<ref>{{#cite:Q1513}}</ref>

Rongzhou: /* Thunderbird in action */

2026-09-01T21:22:37Z

Thunderbird in action

← Older revision		Revision as of 21:22, 1 September 2026
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	:enters name, email address\nand password;		:enters name, email address\nand password;
	\|#LightBlue\|Thunderbird (account setup wizard)\|		\|#LightBlue\|Thunderbird (account setup wizard)\|
	:look up server settings\nfor the email domain*;		:look up server settings\nfor the email domain[1];
	if (settings found?) then (yes)		if (settings found?) then (yes)
	:prefill IMAP/POP3 and SMTP\nserver settings;		:prefill IMAP/POP3 and SMTP\nserver settings;
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	<blockquote>		<blockquote>
	~~The~~ lookup uses ~~the email address domain as base, tried in this order~~:<ref>{{#cite:Q1508}}</ref>		[1]: Concretely, the lookup uses a best-effort cascade chain:<ref>{{#cite:Q1508}}</ref>

	# a local configuration file in the installation directory (<code><install-dir>/isp/<domain>.xml</code>), mainly for enterprise deployments;		1. search for a local configuration file in the installation directory (<code><install-dir>/isp/<domain>.xml</code>), mainly for enterprise deployments;
	# the provider's own configuration server, e.g. <code><nowiki>https://autoconfig.</nowiki><domain>/mail/config-v1.1.xml</code> (preferred) or <code>https://<domain>/.well-known/autoconfig/mail/config-v1.1.xml</code>, then the same URLs over HTTP;		2. query the provider's own configuration server, e.g. <code><nowiki>https://autoconfig.</nowiki><domain>/mail/config-v1.1.xml</code> (preferred) or <code>https://<domain>/.well-known/autoconfig/mail/config-v1.1.xml</code>, then the same URLs over HTTP;
	# the '''ISPDB''', the Thunderbird project's central database of server settings (<code>https://autoconfig.thunderbird.net/v1.1/<domain></code>);		3. query the '''ISPDB[2]''', the Thunderbird project's central database of server settings (<code>https://autoconfig.thunderbird.net/v1.1/<domain></code>);
	# a DNS '''MX''' lookup: the mail hoster found in the MX record is itself looked up in the ISPDB;		4. perform a DNS '''MX''' lookup: the mail hoster found in the MX record is itself looked up in the ISPDB;
	~~# guessing~~ common server names (<code>imap.<domain></code>, <code>smtp.<domain></code>, <code>mail.<domain></code>~~), probing~~ for SSL, STARTTLS and encrypted passwords;		5. try common server names such as <code>imap.<domain></code>, <code>smtp.<domain></code>, and <code>mail.<domain></code> and probe for SSL, STARTTLS and encrypted passwords;
	~~# manual configuration, if~~ everything ~~else~~ fails.
			If everything fails, Thunderbird asks user to configure the email account manually.
	</blockquote>		</blockquote>

	<blockquote>		<blockquote>
	'''ISPDB''' is the acronym of the Internet Service Provider Database: a central database hosted by the Thunderbird project, containing server settings for the world's largest ISPs. Most ISPs with a market share of more than 0.1% are included, which lets Thunderbird autoconfigure a large share of users' accounts with no input beyond name, email address and password.<ref>{{#cite:Q1508}}</ref>		[2]: '''ISPDB''' is the acronym of the Internet Service Provider Database: a central database hosted by the Thunderbird project, containing server settings for the world's largest ISPs. Most ISPs with a market share of more than 0.1% are included, which lets Thunderbird autoconfigure a large share of users' accounts with no input beyond name, email address and password.<ref>{{#cite:Q1508}}</ref>
	</blockquote>		</blockquote>

Rongzhou: /* The mail round trip */

2026-09-01T21:15:22Z

The mail round trip

← Older revision		Revision as of 21:15, 1 September 2026
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	=== The mail round trip ===		=== The mail round trip ===

	Incoming mail: Thunderbird connects to the server over '''IMAP''' or '''POP3''',<ref>{{#cite:Q1489}}</ref> downloads new messages into the profile, updates the message database, and notifies the interface. Outgoing mail goes out over '''SMTP'''.<ref>{{#cite:Q1489}}</ref> After a successful send, Thunderbird ~~itself~~ appends a copy of the message to the ''Sent'' folder~~; the destination folder is configurable under Account Settings → ''Copies & Folders''~~.<ref>{{#cite:Q1514}}</ref>		Incoming mail: Thunderbird connects to the server over '''IMAP''' or '''POP3''',<ref>{{#cite:Q1489}}</ref> downloads new messages into the profile, updates the message database, and notifies the interface. Outgoing mail goes out over '''SMTP'''.<ref>{{#cite:Q1489}}</ref> After a successful send, Thunderbird appends a copy of the message to the ''Sent'' folder.<ref>{{#cite:Q1514}}</ref>

	<uml>		<uml>

Rongzhou: /* The calendar round trip */

2026-09-01T21:14:31Z

The calendar round trip

← Older revision		Revision as of 21:14, 1 September 2026
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	=== The calendar round trip ===		=== The calendar round trip ===

	Thunderbird's calendar component (the ~~<code>~~calendar~~/</code> directory, formerly the~~ Lightning extension)<ref>{{#cite:Q1494}}</ref> stores events and tasks locally in a SQLite database, the file <code>local.sqlite</code> in the profile.<ref>{{#cite:Q1512}}</ref> Network calendars sync with remote servers over '''CalDAV''' (RFC 4791), using '''iCalendar''' (RFC 5545) as the data format, so the same calendar can be shared across devices and clients.<ref>{{#cite:Q1509}}</ref> Invitations travel by email as .ics attachments, handled with '''iTIP''';<ref>{{#cite:Q1509}}</ref> accepting an invitation adds the event to the calendar and sends the reply back.		Thunderbird's calendar component (formerly the calendar Lightning extension)<ref>{{#cite:Q1494}}</ref> stores events and tasks locally in a SQLite database, the file <code>local.sqlite</code> in the profile.<ref>{{#cite:Q1512}}</ref> Network calendars sync with remote servers over '''CalDAV''' (RFC 4791), using '''iCalendar''' (RFC 5545) as the data format, so the same calendar can be shared across devices and clients.<ref>{{#cite:Q1509}}</ref> Invitations travel by email as .ics attachments, handled with '''iTIP''';<ref>{{#cite:Q1509}}</ref> accepting an invitation adds the event to the calendar and sends the reply back.

	<uml>		<uml>

Rongzhou: /* Components and interactions */

2026-09-01T21:10:33Z

Components and interactions

← Older revision		Revision as of 21:10, 1 September 2026
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	CHATPROTO --> NECKO : chat protocols		CHATPROTO --> NECKO : chat protocols
	MAILNEWS --> MAILSVR : IMAP / POP3 / SMTP		MAILNEWS --> MAILSVR : IMAP / POP3 / SMTP
	CALBACK --> CALDAVSVR : ~~calendar sync~~		CALBACK --> CALDAVSVR : CalDAV/WebDAV
	CHATPROTO --> CHATSVR : chat servers		CHATPROTO --> CHATSVR : chat servers
	APPMOD --> ISPDB : autoconfig lookup		APPMOD --> ISPDB : autoconfig lookup

RonzzWikiCowriterAI: Prevent MediaWiki auto-linkifying the example autoconfig URL placeholder; AI-assisted (RonzzWikiCowriter) (via update-page on MediaWiki MCP Server)

2026-09-01T20:53:05Z

Prevent MediaWiki auto-linkifying the example autoconfig URL placeholder; AI-assisted (RonzzWikiCowriter) (via update-page on MediaWiki MCP Server)

← Older revision		Revision as of 20:53, 1 September 2026
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	# a local configuration file in the installation directory (<code><install-dir>/isp/<domain>.xml</code>), mainly for enterprise deployments;		# a local configuration file in the installation directory (<code><install-dir>/isp/<domain>.xml</code>), mainly for enterprise deployments;
	# the provider's own configuration server, e.g. <code>https://autoconfig.<domain>/mail/config-v1.1.xml</code> (preferred) or <code>https://<domain>/.well-known/autoconfig/mail/config-v1.1.xml</code>, then the same URLs over HTTP;		# the provider's own configuration server, e.g. <code><nowiki>https://autoconfig.</nowiki><domain>/mail/config-v1.1.xml</code> (preferred) or <code>https://<domain>/.well-known/autoconfig/mail/config-v1.1.xml</code>, then the same URLs over HTTP;
	# the '''ISPDB''', the Thunderbird project's central database of server settings (<code>https://autoconfig.thunderbird.net/v1.1/<domain></code>);		# the '''ISPDB''', the Thunderbird project's central database of server settings (<code>https://autoconfig.thunderbird.net/v1.1/<domain></code>);
	# a DNS '''MX''' lookup: the mail hoster found in the MX record is itself looked up in the ISPDB;		# a DNS '''MX''' lookup: the mail hoster found in the MX record is itself looked up in the ISPDB;

RonzzWikiCowriterAI: Implement HTML-comment revision advices: redraw components diagram with SQLite, complete the account autoconfig lookup chain, single-lane mail round trip with Sent-copy clarification, add calendar round trip section; AI-assisted (RonzzWikiCowriter) (via update-page on MediaWiki MCP Server)

2026-09-01T20:51:55Z

Implement HTML-comment revision advices: redraw components diagram with SQLite, complete the account autoconfig lookup chain, single-lane mail round trip with Sent-copy clarification, add calendar round trip section; AI-assisted (RonzzWikiCowriter) (via update-page on MediaWiki MCP Server)

Show changes

Rongzhou: /* A regular rapid release schedule */

2026-09-01T20:46:35Z

A regular rapid release schedule

← Older revision		Revision as of 20:46, 1 September 2026
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	Thunderbird is built from day one to support extensions. Its extensibility has long been a core selling point. However, in older versions, add-ons broke with nearly every release, mostly due to backward incompatible API changes. To mitigate the issue, the project gradually phased in a dedicated '''MailExtensions''' framework based on standard WebExtensions technology, powered by stable, permission-gated APIs dedicated to add-ons since 2018.<ref>{{#cite:Q1496}}</ref> In 2020, with the release of version 78, MailExtensions become the only sanctioned framework for Thunderbird extensions.<ref>{{#cite:Q1501}}</ref>		Thunderbird is built from day one to support extensions. Its extensibility has long been a core selling point. However, in older versions, add-ons broke with nearly every release, mostly due to backward incompatible API changes. To mitigate the issue, the project gradually phased in a dedicated '''MailExtensions''' framework based on standard WebExtensions technology, powered by stable, permission-gated APIs dedicated to add-ons since 2018.<ref>{{#cite:Q1496}}</ref> In 2020, with the release of version 78, MailExtensions become the only sanctioned framework for Thunderbird extensions.<ref>{{#cite:Q1501}}</ref>

	=== A regular rapid release schedule ===		=== A regular&rapid release schedule ===

	Since 2024, Thunderbird adopted Firefox's rapid release model: security and stability patches on demand, typically every two weeks; a new major version every 4 weeks; a new extended support release every year, typically in July.<ref>{{#cite:Q1495}}</ref> The model ensures that new features can roll out rapidly to users without compromising long-term stability for users who value it.		Since 2024, Thunderbird adopted Firefox's rapid release model: security and stability patches on demand, typically every two weeks; a new major version every 4 weeks; a new extended support release every year, typically in July.<ref>{{#cite:Q1495}}</ref> The model ensures that new features can roll out rapidly to users without compromising long-term stability for users who value it.