New: translate only the selected part of a message (select text, then use the Translate button or "Translate selection" in the right-click menu).
New: translate your own text before sending. In the compose window, the "Translate before sending" button translates what you wrote into a language of your choice (by default the language of the message you reply to). You can keep your original text below the translation, and Undo steps back, all the way to the text as you typed it. Quotes and your signature are left unchanged, and nothing is sent automatically.
Better translations: whole paragraphs are translated together (the sentence is no longer cut into pieces at bold text or links), and the formatting and links are kept. File names, paths, e-mail addresses and URLs inside sentences are protected, the hard-wrapped lines of plain-text emails are joined into paragraphs before translating, and long texts are no longer cut after abbreviations or ordinal numbers.
New: your own list of names that must never be translated, with an optional advanced mode for regular expressions.
New: optional additional translation services with your own key (DeepL, MyMemory) and an optional backup chain, both off by default. A progress indicator with a Cancel option, and the status line names the service that translated.
Privacy: the language-suggestion badge is now off by default (opt-in in Settings).
Fix: the toolbar button label resets when you switch to another message.
20 interface languages.

1.1.1: Fixes plain-text emails: their text was skipped (it sits in a "pre" block), so only bold/quoted/signature parts were translated. Also keeps the spaces and line breaks at the edges of each translated segment, so words no longer run together.
1.1.0: Optional badge on the toolbar button when the message language differs from your target language (never translates automatically). Optional LibreTranslate backend with a server URL you enter yourself. Translation cache is now size-limited.
1.0.4: A malformed translation response no longer aborts the retry.

Fixes translation failing with "Google Translate HTTP 429".

Google stopped serving the endpoint parameter this add-on relied on, which broke
translation for everyone. This release switches to a working endpoint parameter
and makes the add-on far more resilient:
- Failed requests are now retried automatically with a growing delay, instead of
giving up on the first error.
- Messages are sent in fewer, larger requests, so a long email is much less
likely to hit a rate limit. Non-Latin scripts (Chinese, Japanese, Cyrillic,
Arabic) are handled correctly when sizing those requests.
- If the service does rate-limit you, you now get a clear explanation in your own
language instead of a raw "HTTP 429" error.

No new permissions.

The add-on name is now the same in every language ("Web Translate Toggle for
Thunderbird") to fully comply with Mozilla's trademark naming guidelines; the
interface and description remain translated. No functional changes.