[geeks] Poeple misusing a domain name to send spam ...

[der Mouse]

> they have 2 options added to the setup ...one that black holes the
> stuff and an other that just rejects it if it is undeliverable...
> I've chosen option 1 for the non mx record hosts and 2 for the mx
> listed host...

That actually makes sense.  I was writing from the point of view of a
legitimate MX host.  Hosts that are running mailers but are not MX for
anything can reject or bitbucket or whatever you want, since by
definition the only legitimate mail they will be receiving is mail from
hosts with whom they have a private arrangement, and the local-part
should be checked at the world-facing MX host.  (Well, and mail to
their own postmaster addresses, of course.)

The only danger is that something will go wrong and the MX host and the
backend host will have different ideas of which users are valid; that's
the only case I can think of offhand whwere legitimate mail could be
affected by what the backend host does with mail to (its idea of)
nonexistent local-parts.

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