In addition, I would point out that the first three items are already
handled
within the content for some media types (e.g. application/pdf). In
such cases,
inclusion of the same type of information outside of the content can
lead to
one of the following problems (or a combination of the two):
1. the information is redundant, and therefore wastes some bandwidth
2. the information does not match that within the content, leading to
ambiguity
this brings up (for me) the question of where the information about
copyright is obtained in the first place. body part fields are
supplied by the sender (or his UA) but the sender might not be the
copyright holder of the attachment. should the recipient trust the
sender's assertion about such rights? the sender could easily get it
wrong.