RE: Is Return-Path as available as we think?



-----Original Message-----
From: Greg Connor [mailto:gconnor(_at_)nekodojo(_dot_)org]

--Mark Shewmaker <mark(_at_)primefactor(_dot_)com> wrote:


I did not realize that it was preserved in Return-Path:


Interestingly, my sendmail/pop server shows "Return-Path:" (always at the 
very top) but my Exchange server doesn't show Return-Path at all.  Perhaps 
Return-Path: is not consistent.  Sort of bad news for SPF if it isn't.


Quoting RFC2821, section 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
   data.  This use of return-path is required; mail systems MUST support
   it.  The return-path line preserves the information in the <reverse-
   path> from the MAIL command.  Here, final delivery means the message
   has left the SMTP environment.  Normally, this would mean it had been
   delivered to the destination user or an associated mail drop, but in
   some cases it may be further processed and transmitted by another
   mail system.

Now I don't know what version of Exchange you are using, but my Exchange
2000 SP3 has a Return-Path: on your message to the list:

Return-Path: owner-spf-discuss(_at_)v2(_dot_)listbox(_dot_)com

and from cursory glance at my mailbox it seems like they all have a
Return-Path header. You can view it from Outlook by right-clicking
a message, selecting Options and scrolling through the "Internet
headers" message box.

You will NOT see this header for messages that are sent internally
within the Exchange organization, but that's okay, we don't care about
these anyway when dealing with SPF.

-- Arik

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