I pasted scanned legal documentation in an E-mail. I set Thunderbird to send as plain format, so no HTML. Thunderbird omitted the legal documentation from the E-mail. It was treated as markup and left out.
This is not okay. It should always include all images and other files pasted into the E-mail as attachments when sending as plain text. Otherwise, when I wouldn’t be treated courteously like I was, I might end up with legal issues.
I have now discovered the proper checkmark for setting the E-mail to plain text composition. That will help in the future, but the above mistake is a major legal liability.