Mail header registry?

Hi all,

I just surfed to the IANA site expecting to find of registry of mail 
message headers (per rfc822, etc), only to find none.
Is there such a registry?  Should there be?

If there is/was such a registry, should MIME headers be in the same 
registry, or a different one?
FWIW, I think:

(a) such a registry would be a Good Thing

(b) MIME headers should be in the same registry, as they occupy the same 
collision domain in mail messages
#g
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Graham Klyne
(GK(_at_)ACM(_dot_)ORG)