Robert Bonomi bonomi at
Sat Feb 20 21:14:02 UTC 2010

> From at  Fri Feb 19 22:32:48 2010
> From: William Herrin <bill at>
> Date: Fri, 19 Feb 2010 23:32:10 -0500
> Subject: Re: Spamhaus...
> To: Larry Sheldon <LarrySheldon at>
> Cc: nanog at
> On Fri, Feb 19, 2010 at 8:35 PM, Larry Sheldon <LarrySheldon at> wrote:
> > On 2/19/2010 7:20 PM, William Herrin wrote:
> >> "If an SMTP server has accepted the task of relaying the mail and
> >> later finds that the destination is incorrect or that the mail cannot
> >> be delivered for some other reason, then it MUST construct an
> >> "undeliverable mail" notification message and send it to the
> >> originator of the undeliverable mail (as indicated by the
> >> reverse-path)."
> >
> > Does the RFC say what to do if the reverse-path has been
> > damaged and now points to somebody who had nothing
> > what ever to do with the email?
> Hi Larry,
> Re-reading the paragraph I quoted and you repeated, I'm going to say
> that the answer is "yes."

I'll bite.  *HOW* do you send to the _originator_   (as *required* by
the RFC you quoted) of the undeliverable mail,  when the reverse path 
points to 'someone else'?

Note well the exact lanugage used -- it does not say 'the party named
in the reverse path',  the 'claimed sender', 'putative sender' or any 
other similar equivocation that justifies sending to a forged address.
It says "the originator". To me, that can be only iterpreted in _one_
way. To wit: as the party that _actually_ created and transmitted the
message, _regardless_ of what the declared return path is.

Since such a message is 'defective' (not RFC-compliant -- because the
true point -of-origin is *NOT* in the reverse path, as it MUST be for
an RFC-compliant message) on it's face, I will argue that there is no
need to apply the 'required' handling for a 'proper' message to it.

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