On Sun, Aug 03, 2014 at 11:17:30PM +0000, Viktor Dukhovni wrote: > > Summary: Ready with nits. > > I finally read the complete draft, additional suggested changes > (git diff for the .xml document): Sadly, though it is very late in the process, I failed to notice this originally, and must belatedly report a significant issue noted by Wietse Venema. The response code for rejecting a recipient with a nullmx domain and a sender with a nullmx domain are reversed in the draft. Since 521 like 221 and 421 leads to connection drop after the reply, it is only appropriate when the entire envelope will be rejected. Thus 521 goes with rejection of a nullmx sender domain and 550 with a particular nullmx recipient. C: MAIL FROM:<local@nullmx-domain.example> S: 521 5.7.26 Sender address has null MX ... Server drops connection ... C: MAIL FROM:<local@valid-domain.example> S: 250 2.0.0 Sender OK C: RCPT TO:<local@valid-domain.example> S: 250 2.0.0 Recipient OK C: RCPT TO:<local@nullmx-domain.example> S: 550 5.1.10 Recipient domain has null MX ... Transaction continues, sans bad recipient ... -- Viktor.