> On Jul 14, 2016, at 7:00 PM, Suresh Ramasubramanian <ops.li...@gmail.com> > wrote: > > On 15/07/16, 6:33 AM, "mailop on behalf of Mark Foster" > <mailop-boun...@mailop.org on behalf of blak...@blakjak.net> wrote: > >> Why would any other preference MX exist for a domain not intended to >> be used for email? > > They shouldn’t. Normally. But what if they do?
Then delivery to the other MXes will likely be tried according to the normal rules (and be outside the scope of 7505). Null MX is only useful if it's the only MX for a domain. The weight of the null MX record doesn't really matter. "MX 0 ." is more an idiom than a strict template that must be followed. RFC 7505 extends that slightly by saying that your 7505-aware smarthost or MX might want to use a specific 5xx errors and enhanced status codes to flag a null MX, but that's icing on top of the existing 5321-implied gross behaviour. Cheers, Steve _______________________________________________ mailop mailing list mailop@mailop.org https://chilli.nosignal.org/cgi-bin/mailman/listinfo/mailop
