When I compose email messages, I want them to be plain text only. In older versions of Thunderbird, this worked fairly well, but in new versions, even though the message is sent as plain text, it is not the same text that I type into the editor. For example, if I begin a line with "> " (greater-than space) to indicate a quotation, Thunderbird will add another space at the beginning. I once tried to send "-- " (dash dash space, a signature marker) in a message, only to find that Thunderbird replaced the space with a non-breaking space. I didn't ask for that. I want the content of the message that I send be exactly what I type, nothing more, nothing less. No reflowing, no subtle character alternation. Is there a setting to disable those mis-features?