Also, IMHO, it would be useful if, as well as people being able to submit
header entries, email software authors could say which headers their
software uses (ie. reads and/or writes). That way, it would give an
indication of whether a header is actually useful or not, and whether a
non-standard header may be worth making into a standard one.
It might be interesting information, but it shouldn't be taken to indicate
whether deployment of the header is useful or desirable.
Keith