> 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".
It's syntactically illegal according to the ABNF in RFC 5321 itself, which
specifically states:
IPv6-comp = [IPv6-hex *5(":" IPv6-hex)] "::"
[IPv6-hex *5(":" IPv6-hex)]
; The "::" represents at least 2 16-bit groups of
; zeros. No more than 6 groups in addition to the
; "::" may be present.
> 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).
It may be the source, but the formal syntax specified in the document at hand
has to be the definitive one.
> 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".
No, what's silly is your argument that the ABNF in the actual specification of
how mail clients and servers are supposed to behave isn't the definitive
definition.
> BTW, RFC 5321 still contains the language about
> " if the verification fails, the server MUST NOT refuse to accept a
> " message on that basis.
And that language appears in the context of checking that the IP literal
in the HELO/EHLO actually corresponds to the IP address of the client. It
has nothing to do with syntactic validity.
> so IMHO enforcing any particular interpretation of what an IPv6
> address literal should look like is double-plus-ungood.
Then you should be arguing for a change in RFC 5321, because it is *very*
clear that this usage is not allowed.
Ned