It is almost certainly Yahoo email that is turning it into HTML, because this one was as well. But I have deleted it already.
The GUI/CLI mention was not meant to say you were using CLI. It was that so many people say you aren't a "real Drupaller" unless you use Drush (CLI) or do Git via a CLI. I choose not to; that is my preference.
Likewise, I prefer "top posting" because I can get right to the most current part without scrolling. I would imagine smart phone users would prefer that as well. I don't have one, so I don't know for sure.
This is one area where I think Microsoft wins. In Outlook you can set a format in the contact record. I wish Yahoo did that. It requires a conscious effort in Yahoo, which I don't always think about since 90% of my contacts prefer HTML. Nancy Injustice anywhere is a threat to justice everywhere. -- Dr. Martin L. King, Jr.