On 2/26/21 2:10 PM, b...@uu3.net wrote: > Hmm right... Somehow I tought that having that special Null MX > will silently discard message... I dont know why... > > So, RFC 7505 is pretty much even pointless in my opinion. > You have to do more.. to pretty much achieve the same.. > Its just easier to not having MX on subdomains that does not serve > as email destinations.. Less records in DNS..
It should mean that there is no attempt to deliver email, even if the domain has an A or AAAA record. > > > ---------- Original message ---------- > > From: Grant Taylor via NANOG <nanog@nanog.org> > To: nanog@nanog.org > Subject: Re: Newbie Question: Is anyone actually using the Null MX (RFC 7505)? > Date: Fri, 26 Feb 2021 12:03:37 -0700 > > On 2/26/21 11:46 AM, b...@uu3.net wrote: >> Well, I bet my legacy system will bounce it for example... > What specifically is the bounce? > > I thought the purpose of the Null MX was to do two things: > > 1) Provide as an MX that can't be connected to. > 2) Serve as a signal to things that know how to interpret it that no mail is > to > be expected. > > I would expect that some server, if not the MSA, /would/ generate a bounce > /because/ the email to the domain is undeliverables. > >> I cant speak about Sendmail, qmail, Exim.. when they started supporting it. > My Sendmail boxes have been dealing with the Null MX just fine. The > aforementioned bounce is /expected/ to tell the sender that the destination > address is bad. > >> So, In my opinion changing already working standards in a way >> that they arent full compat with old systems is imo bad aproach. > IMHO there is little, if any, effective difference between the Null MX and an > MX > pointing to an unresolvable name or an non-routed IP. They cause a hard / > fast > failure in an early upstream MTA thus induce a bounce. > > Depending on the MSA, the delivery problem may even be presented to the user > as > they are submitting the message to the MSA. > > > > -- > Grant. . . . > unix || die >
