Re: [Ietf-message-headers] Provisional Registration for "Wrong-Recipient" mail header

[Graham Klyne <[e-mail]>]

(NOTE: I've been asked to review this as IANA's designated reviewer, but these 
comments are provided in a private capacity and don't constitute part of my 
formal response to IANA, which is to allow provisional registration.)

I have some comments about the design of this:

1. It seems to me an odd choice to use HTTP for notifications as part of the 
email protocol. I would have thought that something more like a DSN/MDN message 
response (possibly with an associated MIME type for conveying details) would be 
more appropriate for email. One of email's characteristics is that it doesn't 
depend on an always-on Internet connection, but requiring HTTP POST does. Mail 
clients in particular are likely to be used without there being an available 
Internet connection (cf section 5.2).

2. I would like to see a formal syntax (preferably using 
https://datatracker.ietf.org/doc/html/rfc5234) for the header field to be 
included with this specification. That specification could refer to the URI 
production in https://datatracker.ietf.org/doc/html/rfc3986. It took me a little 
hunting to figure that the field content consists of an HTTPS URI.

3. The example given in section 7 actually contradicts the HTTPS URI requirement 
in section 5.1. An HTTPS URI does not include enclosing "<...>" characters. 
(This sort of problem would be more easily noticed if working with a formal 
syntax specification.) There's noting wrong with including enclosing "<...>" in 
the header field, but if that's what you want it needs to be more clearly specified.

#g