To me, a suitable spec would be something like:
List-Unsubscribe
-----------------
That's it.
Sure, that's it for that one.
Now write a spec for the "Sender" header field.
Maybe if we'd had this proposed 'registry' when 'Sender' was being put into
the standards then it wouldn't have been the same problem it is today... :-)
And then look at all the cases where it's been done wrong over the years
(and understand why X-Sender exists). Some fields are easy to explain,
easy to implement right, and have been a smooth sail.
Most good ideas for message headers are quite easy to specify (Subject,
Date, From, To, etc :-) ). If they're complicated to write a spec for,
maybe they need re-thinking. IMHO the current requirements for making an
RFC or a draft in the 'proper' formal format are quite intimidating for
most people, and having an easier way of *proposing* a new header would be
a good idea.
One way of stopping abuse of a registry would be to 'authorise' people to
be able to add stuff to it (eg, if you want to add a new header you have to
get a login by proving that you are an email software producer (easy to do,
just tell someone your website..)). Then, if there's abuse from that
company, ban them from registering more headers.
I don't see that fear of 'abuse' should be a hindrance to the idea of a
'registry' as it's quite easy to prevent.
Paul VPOP3 - Internet Email Server/Gateway
paul(_at_)pscs(_dot_)co(_dot_)uk http://www.pscs.co.uk/