You missed the point RFC 5321 SMTP clients have to operate with RFC 2821 SMTP servers when sending address literal in the HELO/EHLO. Code doesn't magically get updated when the spec is updated. It takes years for changes to trickle through. The code has to be written, then it has to be deployed. [The who SPF issue is about a WG that is too impatient to wait for the updated code, that has been written, to be deployed. That will happen as OS's get update / replaced.] While RFC 4291 relaxed the address syntax, RFC 5321 didn't because to do so would break interoperability. RFC 5321's address literals are a subset of RFC 4291's permittable address formats. So there is nothing wrong with referencing RFC 4291. Mark In message <20130507012924.GX23227@verdi>, John Leslie writes: > Mark Andrews <marka@xxxxxxx> wrote: > > > > Apples mail client is broken [IPv6:2001:df9::4015:1430:8367:2073:5d0] > > is not legal according to both RFC 5321 and RFC 2821 which is all > > that applies here. > > I was until today unaware how strong the feelings are on this > "one-or-more" vs. "two-or-more" issue. I do not expect to change > anybody's mind. :^( > > But I do object to calling that EHLO string "not legal". > > The 5321 reference names RFC 4291 as the source of address syntax > (even if it gives BNF which says "two or more" if you delve deeply > enough). > > RFC 4921 is clear about saying "one or more". The Errata posted > against it claiming it should say "two or more" have been rejected. > It is silly to argue under these conditions that Apple's EHLO string > is "not legal". > > BTW, RFC 5321 still contains the language about > " if the verification fails, the server MUST NOT refuse to accept a > " message on that basis. > > so IMHO enforcing any particular interpretation of what an IPv6 > address literal should look like is double-plus-ungood. > > ==== > > To the casual observer, it looks as if RFC 4291 relaxed a previous > "two or more" requirement, but there are folks who don't want to > accept that relaxing. > > One can accept the idea that this relaxing has failed, yet still > observe "liberal in what you accept" as trumping it. I truly wish the > folks in the "two or more" camp would do so! > > -- > John Leslie <john@xxxxxxx> -- Mark Andrews, ISC 1 Seymour St., Dundas Valley, NSW 2117, Australia PHONE: +61 2 9871 4742 INTERNET: marka@xxxxxxx