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English (en-US) Language Pack

English (en-US) Language Pack

Rated 2 out of 5 stars (11)
149,899 users

Italiano (it) Language Pack

Italiano (it) Language Pack

Not yet rated
62,254 users

Lightning Calendar Tabs

Displays tabs which allows quick navigation between time periods in Lightning calendar. All views of calendar are supported. Color of tab texts can be adjusted.

Rated 4 out of 5 stars (25)
28,634 users

Diccionario español Argentina

Spanish dictionary for Argentina.

Rated 4 out of 5 stars (93)
13,314 users

British English Dictionary

British English Dictionary R1.19 for Firefox, Thunderbird and SeaMonkey by David Bartlett.

To enable, right-click in a multi-line text box, select "Languages", then "English / United Kingdom".

Rated 3 out of 5 stars (413)
2,392 users

Ukrainian dictionary

Ukrainian (uk-UA) spellchecking dictionary

Rated 5 out of 5 stars (58)
11,048 users

General Catalan dictionary

Free Catalan (general version) spelling dictionary.

Rated 4 out of 5 stars (40)
15,270 users

Japanese (ja) Language Pack

Japanese (ja) Language Pack

Rated 3 out of 5 stars (3)
51,459 users

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)
9,624 users

Emoji

Add emojis to your e-mails.

Rated 4 out of 5 stars (64)
27,448 users

Addressbooks Synchronizer

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

Rated 4 out of 5 stars (82)
29,351 users

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)
10,047 users

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 (72)
14,343 users

Check and Send

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

Rated 4 out of 5 stars (50)
23,086 users

Russian Hunspell dictionary

Создан на основе словаря Лебедева. Файл аффиксов постепенно переписывается, словарь ежедневно пополняется. Релиз выкладывается один раз в месяц первого числа.

Rated 3 out of 5 stars (65)
11,232 users

Confirm-Address

Confirm E-mail address before sending mail

Rated 4 out of 5 stars (75)
21,576 users

Hungarian Dictionary

This extension is based on László Németh's Hungarian Dictionary

Rated 4 out of 5 stars (56)
10,476 users

Český slovník pro kontrolu pravopisu

Slovník pro kontrolu pravopisu pro aplikace Mozilla

Rated 4 out of 5 stars (36)
17,899 users

German Dictionary, extended for Austria

German dictionary (new Orthography) for spellchecking in Mozilla products, extended with Austrian words

Rated 5 out of 5 stars (22)
5,796 users

Russian (ru) Language Pack

Russian (ru) Language Pack

Rated 3 out of 5 stars (5)
50,991 users