What is Communications Data?

[Ian G Batten]

On Fri, 15 Nov 2002, Rodney Tillotson wrote:

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> At 14/11/2002 16:33 +0000, Ian Batten wrote:
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> > In SMTP land, Return-Path: is typically only used by final delivery
> > agents to take the envelope MAIL FROM: and place it somewhere that the
> > end recipient can get at it.  It has no formal status as a header.
> 
> Not sure what "no formal status" means. RFC2821 says in 4.4:
> 
> > When the delivery SMTP server makes the "final delivery" of a
> > message, it inserts a return-path line at the beginning of the mail

Exactly.  A Return-Path: will not be passed along an SMTP connection, or
if it does it has no meaning.  When final delivery takes place, at which
point the presumption is that the message is now now longer travelling
through SMTP, the information that was in the SMTP FROM: is retained in
that header.  It's not part of SMTP, because inserting a Return-Path:
header into mail travelling through SMTP will not override the use of
the MAIL FROM: for error reporting.

ian