On 2012-06-04, David Diggles <da...@elven.com.au> wrote: > I was just thinking surely resending from a different IP breaks the RFC for > SMTP? > > Then I did some googling, and found this. > http://bsdly.blogspot.com.au/2008/10/ietf-failed-to-account-for-greylisting.html > > Thanks, Peter. > > So now it is 4 years later, has anything happened? > >
No. It is perfectly valid, and even somewhat normal, to resend from different addresses. Whether this is by pools of senders with shared queues, or whether it's by pools of internal MXes behind NAT boxes, it definitely happens. The majority of such senders try and keep within the same /24. The greylisting.org/puremagic.com whitelist was specifically only for senders which did not follow this (they refused to add sender pools to the list if they stuck within /24). Though that's largely irrelevant as their list hasn't been updated in 6 years..
