rfc2822bis -- adding clarifying Sender: text

This is not about a problem with the current text, but rather a bit of 
confusion started by RFC 733 that might benefit from some clarifying language.

I see the confusion rear its head regularly and think it time to have some 
text that tries to help people understand the difference between information 
and its encoding...

Current:

> 3.6.2.  Originator fields
>    The originator fields indicate the mailbox(es) of the source of the
>    message.  The "From:" field specifies the author(s) of the message,
>    that is, the mailbox(es) of the person(s) or system(s) responsible
>    for the writing of the message.  The "Sender:" field specifies the
>    mailbox of the agent responsible for the actual transmission of the
>    message.  For example, if a secretary were to send a message for
>    another person, the mailbox of the secretary would appear in the
>    "Sender:" field and the mailbox of the actual author would appear in
>    the "From:" field.  If the originator of the message can be indicated
>    by a single mailbox and the author and transmitter are identical, the
>    "Sender:" field SHOULD NOT be used.  Otherwise, both fields SHOULD
>    appear.

Add after this:

    Note: The Sender (responsible agent) information is always present. The 
absence of the "Sender:" field merely means that the information is redundant 
with the "From:" field, so it is not redundantly encoded into a separate 
field. The absence of the "Sender:" field sometimes confuses readers into 
believing that the Sender responsible agent information has not been specified 
explicitly.


d/
-- 

   Dave Crocker
   Brandenburg InternetWorking
   bbiw.net