How to set line break with HTML composed e-mail in Thunderbird?

I cannot make Thunderbird break lines in my E-mail to specified length when they are composed in HTML, even after I did the following:

the "mailnews.wraplength" in Edit->Preferences->Advanced->Config Editor is set to 80, as well as the boolean "mail.wrap_long_lines" which is set to true. Also, I have set the "mail.compose.wrap_to_window_length" to false. Still, lines in the HTML composed E-mail are broken at window length, even after restarting Thunderbird.

I have installed the "Toggle Text Wrap" addon and it's working fine, but this means I need to compose E-mail in text mode. Is it possible to make Thunderbird split up endless, non-readible lines when using composing in HTML and with pre-scribed fixed width?

Edit: Is there a way to set the window size when I start composing e-mails, so that the line breaking that is somehow fixed to the window size, works on a smaller window?

Solution 1:

The answer to the question in the topic is:

In order to set break for html you will have to use <br> tag, for simple text you will have to use \n.

For your edit question, the way I may think of is using a div which contains your text, you can give it a width (and a height if you would like to).

<div style="width:400px;" >You text here! </div>

I hope it helps.