On 25 Jun 2013, at 18:01, "John Levine" <jo...@iecc.com> wrote:
> There is a somewhat popular convention that if a domain publishes an > MX like this: > > whatever.example MX 0 . > > it means the domain does not receive mail. Well yes. But it only "works" as long as there are no A or AAAA records for . in the root zone. If that was ever to change, anyone who adopted this Bad Idea will be in for a nasty surprise. > I don't see anything about it in the postfix docs. Does Postfix > do anything special with such an MX? Or if not special, does it > fail deliveries? I don't see why any MTA would need or want to have special code to handle this. Or to deploy such code without a proper RFC underpinning it. [If there was an I-D about this which died all those years ago, that should give a fairly strong hint what the IETF thought of the idea.] IMO there's no justification to make MTAs treat the domain name(s) in the RDATA of some MX records as "special cases" which should be handled differently from other domain names that may be found there. If someone doesn't want a domain name to get email, the solution is simple. Don't start an SMTP listener. For bonus points, don't publish MX records for the domain either. Avoid having A or AAAA records too, or at least make sure they go somewhere that doesn't listen for SMTP.
