Excerpts from internet.ietf-822: 25-Apr-91 Re: Comments on Draft RFC
Vincent Lau(_at_)eng(_dot_)sun(_dot_)com (1843)
The value in Content-Label is controlled by the user, but Message-ID
is not. The information in Content-Label is intended for human being.
Now I'm really confused. What, in this case, is Content-Label actually
for? I had assumed its primary purpose was to allow certain parts to
reference each other to form complex structured multipart mail, but this
statement implies that I've entirely missed your motivation.