Re: OT: 5xy - Do we need a "I MEAN IT!" do not retry response code?

John C Klensin writes:
> --On Wednesday, May 02, 2007 12:14 PM +0200 "Peter J. Holzer" 
> <hjp-ietf-smtp(_at_)hjp(_dot_)at> wrote:
> > "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.
And it only needs to work for a few minutes following MAIL FROM in order 
to get >99% of NDNs.
Arnt