--On Wednesday, May 02, 2007 12:14 PM +0200 "Peter J. Holzer"
<hjp-ietf-smtp(_at_)hjp(_dot_)at> wrote:
I didn't catch well what it meant by "hard and soft bounces"
and "BounceBack Messages?" Does that main a real
accept/bounce transaction or a 5xy response? or both?
I'm not sure either. "hard and soft bounces" could be either
5xx and 4xx respectively, or a "soft bounce" could be a
"couldn't deliver for $n hours, will keep trying" message.
I suspect 5yz and 4yz, although, if they are looking at NDNs,
they might even be looking at extended codes. Or a hard bounce
might be an SMTP reject and a soft bounce an NDN
"BounceBack Messages" are probably NDNs. I find this
interesting, because it means that to use this software (or at
least this feature) the spammer has to use a genuine
reverse-path.
Well, the return-path needs to be genuine only for NDNs. It is
irrelevant for SMTP-time rejections as long as those are
considered "hard". It does suggest that greylisting and
silently dropping messages are, with regard to this technique,
pathological: doing either gets you more spam; three clear
rejections in a row and the noise stops.
john