Sure, but in this case wouldn't deferring to the end systems argue in favor of
allowing end systems to
make the decision as to whether their private information should be exposed?
You can expose whatever you want, but if you expect anyone to accept
your mail, you will follow the rules set by the recipient systems.
This has been the way that mail has worked for many decades, and it's
not going to change now.
For a lot of the changes proposed here, the practical effect would be
that anyone foolish enough to implement them would find that the set
of systems accepting their mail shrinks dramatically. For anyone
planning self-righteous complaints that you HAVE to accept my mail
because I'm following some standard or other, don't bother. See, for
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