Дополнения

Remove Duplicate Messages от Eyal Rozenberg

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

Mail Redirect от Onno Ekker, Pawel Krzesniak

Позволяет перенаправлять ("перепослать") сообщения другим адресатам.

Примечание подборщика なるべく余計な手を加えずにそのまま転送するために。

CompactHeader от jmozmoz

Add symbol in header plane to switch between compact and expanded view. Work only for Thunderbird 68.0 and older. Currently, there are no plans to update this for newer versions.

Quote Colors от Malte Ruecker

Quote Colors allows you to select text and background colors of different quote levels which are applied when reading or printing mail/news messages. Additionally, you can choose between graphical and traditional plain text quoting display mode.

Примечание подборщика 標準のスタイルよりこっちの方が自分は見やすい。

Thunderbird Message Filter Import/Export Enhanced от kounavi

Thunderbird Message Filter Import/Export Enhanced is a compatibility port of Wind Li's add on.
Original add on here: https://addons.mozilla.org/en-US/thunderbird/addon/thunderbird-message-filter-imp/

Thunderbird Message Filter Import/Export от Wind Li

Thunderbird Message Filter Import/Export - это расширение thunderbird/mozilla для Импорта/Экспорта фильтров сообщений.

Примечание подборщика 常用は言い過ぎかも。1回使ったらもう使わない類のアドオンだし……

Correct Identity от ldreier, Dennis Verspuij

Ever sent mail from the wrong email address because you forgot to select the correct identity?

Примечание подборщика プライベートなメールと仕事のメールとを同じ所にぶち込んでるので、差出人を選択し忘れるのを防ぐために。

Folderpane Tools от chuonthis, Philip Chee

Allows for customization of the folder pane. Accounts can be rearranged and the startup folder can be chosen.

Примечание подборщика 常用は言い過ぎかも。1回使ったらもう使わない類のアドオンだし……

Priority Switcher от H.Ogi

Change priority of the received messages from the toolbar button and the context menus...

Before Tabs Toolbar от Paenglab

Adds a toolbar before the tabs.

Ruler Bar от Piro (piro_or)

This appends a ruler to the mail composition window.

Примечание подборщика なんとなく、あると安心する。無くても使える。そんな機能。

XUL/Migemo от Piro (piro_or)

This provides dictionary-assisted search (Migemo search) and regular expression powered search for "find in this page" and other features.

Примечание подборщика 対応させてみたので入れてるけど、いまいち自分でも使ってない。

CuteMenus - Crystal SVG от mrtech, Static_Nexus, другие

Note from Mozilla: This add-on has been discontinued. Try Menu Icons Plus instead.

Adds icons to all menus along with some other features...

Примечание подборщика メニューの視認性が上がる。

Sync On Arrival от Michael Buschbeck

Downloads new message headers (and bodies, if configured) immediately when Thunderbird detects new messages in an IMAP folder - that's more or less what the "download_on_biff" preference promises to do, but somehow fails to deliver...

Примечание подборщика IMAP使うならこれがないとやってらんないと思う。