I believe they meant users changing their mx for an existing domain, when moving
to fastmail for example. Not necessarily a new domain, though I guess they can't
really differentiate those technically. So the policy would also apply to new
domains. Not entirely sure that this is the solution, but I get it.
Louis
Op dinsdag 10 oktober 2023 om 12:25, schreef Alessandro Vesely via mailop:
> On Mon 09/Oct/2023 08:23:33 +0200 Robert Mueller via mailop wrote:
> > >> I see that current setup might be useful in case some user changes MX >>
> before the domain is activated at Fastmail, in which case giving 4xx >> could
> make sense. But it is not right to report such re-tries to sender >> score as
> attempts to deliver to non-existing users.
> > > Yes, this is why we 4xx rather than 5xx email sent to an unconfigured
> domain. Many inexperienced email users aren't sure exactly what order to
> change or set things up in and we've seen users lose email before because they
> changed the MX records before adding their domain at Fastmail. The 4xx
> response reduces the chance of lost email.
>
> That's bad.
>
> First, nobody sends an important mail to a new domain without double checking
> its delivery. It is very reasonable to loose a few test messages when you set
> a new domain up.
>
> By 4xx any unconfigured domain, a warning for delayed email can take hours and
> several attempts. A 5xx would result in an immediate DSN, which is much better
> in case of mistyping.
>
> Best
> Ale
> --
>
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