Re: SPF and bouncing

On Tue, 3 Apr 2012, Stuart D. Gathman wrote:
> > So, the answer then is "No.  Unlike the non-SPF case, you won't make
> > anyone angry.  But there's still a substantial risk of double-bounce,
> > which you can avoid by remaining as cautious as if there were no SPF."
>
> What double-bounce?
Semantics problem.  For me, the term "double-bounce" has always meant the
event that is supposed to occur when a normal bounce receives a 5xx
in-transaction or times out: the message goes into a deadletter file on
the last server it reached.

This is still bad for that server, as the deadletter archive will grow
without bound unless an operator checks it from time to time.  If you
just archive to /dev/null, you create the blackhole issue where someone
might never know they mistyped an address.

(And this is a selfish incentive to use backscatter-proof mail
arrangements, even if you aren't afraid of UCEPROTECT's backscatter
DNSBL.)

> By definition, there should never be any bounce to MAIL FROM <>.
There can't be.  To what IP address would you say "EHLO example.org; MAIL
FROM: <>; RCPT TO: <>; DATA ..."?

Anyhow, such silliness is not what I meant by "double-bounce".


Although I'd note that disabling SMTP's anti-loop mechanism by using the
failed address instead of <>, would avoid the whitelist problem I'm
discussing.  No, I'm *not* recommending anyone do that!

SWK would fix it by allowing the sender to *simultaneously* publish <> for
return-path purposes only and the failed address for whitelist purposes
only.

---- Michael Deutschmann <[email protected]>