Switch between HTML and Plain Text compose in Thunderbird

[doctorgonzo]

I thought I would post this since it seems to be a well-kept secret in Thunderbird documentation.

You can choose whether you want to compose new e-mail messages in HTML or plain text in your e-mail account settings in Thunderbird, but what if you temporarily want to switch to the other? Unlike in other e-mail clients, it appears to be impossible to change the format once you have started composing your message, and changing your account settings prior to composing just one e-mail is a pain. Fortunately, there is a better solution:

Hold down "Shift" when you click on the "Compose" button and you will get the opposite of your default choice. Instead of plain text, you will get HTML, or vice versa.