I use Thunderbird to communicate about programming work. In such Emails, routinely code snippets, variable names, function names, etc. appear, which generally do not form valid words under the rules of any given language - if only by the use of camelCase In hand-written HTML, these would be formatted using the <code/> and <pre/> tags. In Thunderbird, these are supported through the "Preformat" paragraph style in Format → Paragraph → Preformat, or via a hotkey sequence Alt+O, P, F. the "Code" text style in Format → Text Style → Code, or via a hotkey sequence Alt+O, S, O. Additionally, there is the more easily accessible <tt/> tag, which is supported via the hotkey Ctrl+T, or via Format → Text Style → Fixed Width. However, spell checking is applied to these, even though it is almost certainly going to produce false positives. Please consider excluding these from spell checking. A similar feature seems to already exist in Thunderbird; Block quotes are already excluded from spell checking. Demonstration screenshot
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