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Provider for Google Calendar

Allows bidirectional access to Google Calendar

Rated 3 out of 5 stars (1,651)
181,583 users

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British English Dictionary (Marco Pinto)

A fork of Mark Tyndall's add-on, based on David Bartlett's
British Dictionary R1.19 for Firefox, Thunderbird and SeaMonkey.

V3.3.4 has 140 000+ new words and also fixes.

Rated 5 out of 5 stars (83)
162,136 users

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English United States Dictionary

English United States (en-US) Dictionary as shipped with Thunderbird 115 ESR and Firefox 115 ESR.

Rated 4 out of 5 stars (39)
67,685 users

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German Dictionary

German Dictionary (new Orthography) for spellchecking in Mozilla products

Rated 4 out of 5 stars (82)
226,459 users

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Spanish (Spain) Dictionary

Spanish/Spain Dictionary

Rated 4 out of 5 stars (167)
57,760 users

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DKIM Verifier Featured

Verifies the DKIM-Signature of an e-mail.

Rated 4 out of 5 stars (45)
17,563 users

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Dizionario italiano

Add support for Italian to spellchecking

Rated 4 out of 5 stars (71)
70,560 users

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Send Later

True "Send Later" functionality to schedule the time for sending an email.

Rated 5 out of 5 stars (263)
98,033 users

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Remove Duplicate Messages

Search and remove messages which are the same as other messages in your mail folders (referred to as duplicates or dupes).

Rated 4 out of 5 stars (292)
91,084 users

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Woordenboek Nederlands

Dutch dictionary with wordslist from OpenTaal.

Rated 3 out of 5 stars (70)
22,618 users

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Signature Switch

Switch the signature on/off or choose a new one from your predefined set.

Rated 4 out of 5 stars (272)
50,409 users

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Diccionario español Argentina

Spanish dictionary for Argentina.

Rated 4 out of 5 stars (93)
13,356 users

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QuickFolders (Tabbed Folders)

The "Swiss army knife" of folders. Turn your favorites into tabs - open folders and subfolders, move mails without scrolling around or searching. powerful + easy.

See new mail at a glance after automatic filtering - supports quickFilters addon!

Rated 5 out of 5 stars (188)
14,270 users

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Ukrainian dictionary

Ukrainian (uk-UA) spellchecking dictionary

Rated 5 out of 5 stars (58)
8,637 users

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General Catalan dictionary

Free Catalan (general version) spelling dictionary.

Rated 4 out of 5 stars (40)
12,060 users

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Canadian English Dictionary

For some reason, Mozilla doesn't have a Canadian localization team, but I know that even the British dictionary doesn't quite cut it for the truly patriotic.

Rated 4 out of 5 stars (82)
8,961 users

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Emoji

Add emojis to your e-mails.

Rated 4 out of 5 stars (64)
23,728 users

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Addressbooks Synchronizer

Synchronizes selected addressbooks with other instances of thunderbird
using local files, webdav servers or imap servers

Rated 4 out of 5 stars (79)
23,543 users

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German Dictionary, classical spelling standards

German Dictionary according to the classical spelling standards for spell-checking in Firefox and Thunderbird

Rated 5 out of 5 stars (20)
9,173 users

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quickFilters

Quickly generate mail filters on the fly, by dragging and dropping mails and analyzing their attributes. Create a filter in less than 10 seconds, it's as easy as: drag, click, click.

By popular demand, supports SORTING filters alphabetically.

Rated 5 out of 5 stars (70)
12,943 users

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