Mail isn't what it used to be. Programs like Thunderbird auto-decide whether to send the mail in text or HTML, and somewhere along there are linebreaks inserted in the messages that I do not insert myself and that do not appear in my Sent folder, which fouls up the layout.
I don't know if it's related, but in the last few weeks, I had lots of problems when answering with Thunderbird to messages originally made with Outlook. I answered with "inline" quotations. Some paragraphs were readable under OL, and some other paragraphs were not ! I thought the problem was coming from the (quite dirty) HTML management in Outlook. But it seems display problems are more around Thunderbird...
The solution is probably to use plain text. I thought it was default on this ML, bit it was not. It is, now.
PS : Another reason not to throw too quickly good old technologies from the last century, HI :-D Newer technologies are not necessarly better :-D
73 de TK1BI