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Provider for Google Calendar

Allows bidirectional access to Google Calendar

Rated 3 out of 5 stars (1,650)
182,867 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)
161,351 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)
68,110 users

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Deutsches Wörterbuch

Deutsches Wörterbuch (neue Rechtschreibung) für die Rechtschreibprüfung in Mozilla-Produkten

Rated 4 out of 5 stars (82)
223,225 users

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Diccionario de Español/España

Diccionario de Español/España

Rated 4 out of 5 stars (167)
57,053 users

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ExQuilla for Exchange

Thunderbird email accounts connecting to Microsoft Exchange Web Services.

Rated 4 out of 5 stars (132)
4,739 users

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DKIM Verifier Featured

Verifies the DKIM-Signature of an e-mail.

Rated 4 out of 5 stars (45)
17,510 users

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Dizionario italiano

Add support for Italian to spellchecking

Rated 4 out of 5 stars (71)
70,676 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)
98,173 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)
91,237 users

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Woordenboek Nederlands

Woordenboek Nederlands met de woordenlijst van OpenTaal.

Rated 3 out of 5 stars (70)
22,122 users

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Lightning Calendar Tabs

Zobrazí záložky, pomocí kterých je možné rychle přepínat aktuální období v kalendáři Lightning. Všechny pohledy kalendáře jsou podporovány. Je možné upravit barvu textů záložek.

Rated 4 out of 5 stars (25)
27,629 users

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Diccionario español Argentina

Diccionario ortográfico de español de Argentina.

Rated 4 out of 5 stars (93)
11,767 users

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Український словник

Український словник перевірки орфографії

Rated 5 out of 5 stars (57)
10,747 users

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Diccionari català (general)

Diccionari ortogràfic lliure català (versió general).

Rated 4 out of 5 stars (40)
11,196 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)
9,131 users

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Emoji

Add emojis to your e-mails.

Rated 4 out of 5 stars (64)
23,682 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)
23,499 users

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Deutsches Wörterbuch (de-DE), alte Rechtschreibung

Wörterbuch deutsch (alte Rechtschreibung) für die Rechtschreibprüfung in Firefox und Thunderbird + alte Rechtschreibung + bisherige Rechtschreibung + klassische Rechtschreibung + bewährte Rechtschreibung + unreformierte Qualitätsrechtschreibung +

Rated 5 out of 5 stars (20)
9,069 users

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Check and Send

Check the message contents and addresses before you send the message...

Rated 4 out of 5 stars (49)
20,226 users

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