> On Jan 4, 2020, at 1:14 PM, Thierry Fournier <[hidden email]> wrote:
> Hi list,
> For my own usage I wrote a new DNS filter which is executed by smtp / lmtp client
> before executing DNS request.
> It allow to force response on MX requests without performing DNS request, or
> force "domain not found” response.
> - For example, I can build MX response to force an email to be routed on my own
> servers in place of the real destination serveur. This is useful for tests.
> - Other example is an easy way to integrate relay on Internet in front of existing
> couple of MTA without changing any configuration and keeping the high availability
> provided by the DNS multiple MX records. (the “relay" transport doesn’t seem to
> allow multiple target).
> - Next example is blacklisting specific domain before performing the DNS request.
> Are you interested by the patch which integrate this functionality in main postfix branch ?
IMHO, all of this can be done in a local (unbound, BIND, ...) resolver. A Postfix MTA
connected to the public Internet, *should* run a local resolver.