Configure Thunderbird to never send (or even try to send) HTML emails

Question

Where can I tell Thunderbird always to send emails as plain-text, and never as HTML-formatted messages? I hate HTML-based email, and always do everything possible to send my emails as plain text.

Thunderbird is always pestering me with questions like "This recipient cannot receive HTML..." or "In order to sign this email, it needs to be converted to plain text..."

Is there a way I can simply say to Thunderbird "Look, old chap, it's all plain text, so don't bother me any more, ever, again"?

Answer 1

One way to accomplish this is to turn off "Compose messages in HTML format", which is under your account settings, in "Composition and Addressing". This will also get rid of the HTML editor, which can be useful even for plain-text messages. (e.g., it nicely formats lists)

The other way which preserves the HTML editing features, but auto-converts to plain text, is Preferences -> Composition -> Send Options -> Text Format, select "Convert the message to plain text" instead of "Ask me what to do".

Answer 2

Tools > Account Settings > Composition & Addressing > Untick "Compose messages in HTML format".