I do not like HTML emails. Because of that, I've set my Thunderbird to compose emails as plain text.

But, in some rare cases, I have to send an HTML email, e.g.:

Hi Your Majesty, the button you are asking for is the one with the plus and the minus on top of each other:

Windows Calculator, with button indicated

Let me know if that helps. Cheers!

Writing such simple stuff into a graphical attachment slows everything down on both sides, so I think in this rare case, HTML can be justified.

Is there any method in Thunderbird to compose a single, one-off email as HTML?

I know that I can configure it to compose all emails as HTML, so using that I would have to switch it on, compose the email and switch it off again. Not good.

  • There is a pertinent feature request I may did up later and link; commenting from mobile to remind myself.
    – Wildcard
    Jul 28, 2019 at 15:56

2 Answers 2


If your default setting is to compose Plain Text emails, hold down the Shift key when you click the Write button or Reply/Reply-All/Forward button. This will open a window to compose an HTML email.

  • 7
    Whoa!!!! :-O
    – Bowi
    Jul 26, 2019 at 12:52
  • That trick is symmetrical: If the default setting is HTML, holding down Shift when clicking composes a Plain Text email.
    – Bowi
    Oct 21, 2020 at 14:31

Another possible solution is to select the box

Account Settings -> Composition & Addressing -> "Compose message in HTML format"

and also select

Tools -> Options -> Send Options -> "Send messages as plain text if possible"

Then when you open a composition window, you'll see the HTML formatting bar (font size, bold, italics, etc.), but Thunderbird will only send your message as HTML if you use one of those options (or if you're replying to an HTML-formatted message). If you compose a plain-text message with no formatting, Thunderbird will detect that and send the message as plain text.

  • Second option is buried in a couple of tabs. Should be Tools -> Options -> Composition tab -> General tab -> Send Options button -> "Send messages as plain text if possible"
    – smitelli
    Jul 27, 2019 at 12:49
  • I think there's also an option whereby it prompts you if it thinks the message isn't convertible (e.g. accidentally pasted in formatted text) thus allowing you to force the message as plain text anyway.
    – Neil
    Jul 28, 2019 at 15:23

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