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Re: Mail/MIME permanent header registrations

2004-04-17 10:08:41


Following approval of the message header registry [1][2], Jacob and I have
been working on a document to contain initial registrations of
standards-track email and MIME headers [3].

Modulo some small editorial fixes, I believe this is ready to request a
last-call (for publication as informational RFC, and subsequent
registration of the entries contained therein).

I agree.


Possibly contentious items are:
   Accept-language[4]

What's there seems reasonable enough to me.

   Encoding (experimental) [5]

The encoding field is an interesting case. On the one hand, it is specified in
an experimental RFC so it does belong in the registry. On the other hand,
actual use of the field varies widely from what's in the RFC. In particular,

(1) Some agents use byte counts in the field, not line counts. (Needless to
   say, this doesn't interoperate well.)

(2) Some implementations, in an effort to provide better name and type
   information, embed filenames in the field.

(3) Support for nesting as well as support for many of the encodings
   specified in RFC 1505 is rare.

And then there's the pesky problem that this whole scheme depends on line or
byte counts, which tend to get disrupted as messages pass through the transport
infrastructure. (Used to be that line folding, and tab expansion caused the
disruption. These days its more likely to be insertion of disclaimers or
charset conversions that cause trouble.)

The current registration text makes it clear that this field has interop
problems, and I personally think that's sufficient.

                                Ned


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