You appear to think numbers (by default in points) are standard practice for defining HTML. They are not in the way you think in HTML and other web related markup languages. It is standard practice in the printing industry to describe fonts in points. It is therefore standard practice to use fonts designated in points for output destined for paper. Word processors are a good example of such a thing. The web, and HTML as the language of the web does not use Fonts designated with a numerical size in points, when it is done it is done either Pixels or using the HTML specified values of 1-7 '''Note''': An 11 pixel font is about 30% smaller than an 11 point font. But the real size difference is relative to the screen and the screen resolution in use. On a Mac Retina dis[play an 11 pixels is only perhaps half of it's point cousin. So then we get to email. Thunderbird uses the smaller and larger analogy for the sizes specified for HTML.that is size 1-7 see http://www.ironspider.ca/format_text/fontsize.htm The newest version of HTML Version 5 will actually remove the font size tag making it a prerequisite that font size information be designated in CSS. CSS is not supported by all popular mail clients. there is a feature comparison here https://www.campaignmonitor.com/css/ Note that Outlook is missing some important elements like font name Then we get to copy and paste. The biggest issue here is people appear to think word processor output and HTML are the same thing. They are not. The reality is that when pasting to HTML it is good practice to paste as unformatteed text. Ctrl+Shjft+V to prevent mismatched fonts and styles. In the case of word for example the word formatted information is converted by word to HTML and placed on the clipboard. When this is pasted to Thunderbird it brings basically the whole document it was pasted from, including the internal path to the document on your PC into Thunderbird's editor. Most of this information is visible only in the message source, but it is massively complex and mostly redundant. Redundant complexity is a recipe for trouble in the most well meant projects. I do not think Microsoft always mean well. Finally you talk about format painter. Is that the patented technology owned by IBM cited here http://www.google.com/patents/US20130290836 How do you propose an open source project with no financial abilities or sources of income pay the license fees for that? An enhancement request was raised in 2008 to allow pasting of format only. https://bugzilla.mozilla.org/show_bug.cgi?id=417157 Perhaps you could vote for it. While it is widely accepted in the Thunderbird community that the editor is dated and requiring serious attention, there are some serious issues to overcome. 1. The editor is actually a Firefox component and development is therefore the responsibility of the much better funded Firefox. Unfortunately about the only use it gets in Firefox is a text dialog like the one you type into on the forum. So they have little or no motivation to fix it. 2. The source code is ancient, mostly written in C++ at Netscape in the last millennia . It is difficult to read and difficult to modify. There are very few people that actually understand it. Not something someone will be volunteering to fix in their spare time really. 3. An attempt was made some 5 years ago to make the editor from a plugin web editor. It turned out to be about 10,000 bugs and barely usable. See the post here https://blog.mozilla.org/labs/2010/09/2756-bugs-found/ This was all done before Mozilla closed their subsidiary Mozilla messaging. as each downgrade of Mozilla support has come along, the editor upgrade has got further and further away. But it is still dear to the heart of many. But it is a lot of work, and without paid staff unlikely to make much progress unfortunately. 4. Thunderbird is a community project. Governed by the Thunderbird council. Mozilla allow the use of their resources, such as this forum and build servers, but they do not do any active development on the project at all. Mozilla is really Firefox, Firefox OS, Firefox for Android and Webmaker. Having said all of that, I think you will find active or open bugs in [https://bugzilla.mozilla.org/ Bugzilla ]for almost everything you mentioned. It is not for lack of interest or ideas. It is a lack of funds that is crippling some parts of Thunderbird's future.