Just had someone send back the header of a message I sent to them from my mail file: when they get it, the from and reply section contains most of what I see in my Notes display, but it's spread out all over their header area, padded out with bunches of spaces n tabs and so forth. I suspect they are using something which strips out everything not plain text (just call me "mr plain text", heh!), and the handy parts of the Mail Experience form like "please respond to…" and so on are coming out mangled.
Is it possible to excercise any control over recipient formatting for plain text? I tried changing the multipart preference in the SMTP config and they claim there's no difference in what they see, so I presume there is some role played in SMTP conversion by the content of the form layout?