One thing I liked about Thunderbird is that if I write an email without explicitly specifying a font in the text editor, the HTML part of this mail doesn’t contain a font name or font size. So the recipient’s email client uses the default font, but it’s still an HTML email and can contain tags like “” (bold text) or images.
I’d be very very happy if there was a way in the eM Client to not select a font for new emails at all or to enable a checkbox like “don’t use a specific font in html emails” (unless I select one in the text editor), so that the default font is displayed in the editor when composing an email, but not written to the HTML source of this email. Could this feature be implemented in the future? That would be nice 
One of the reasons why I ask is: Unfortunately, although I’ve selected a font size that looks fine on Windows (Arial 11 pt.), it’s too large in Apple Mail on macOS. Without an explicit font specification, I think it would be perfect. I didn’t have this problem with Thunderbird in the past, because there was no font in the HTML source code.