> On Sep 11, 2017, at 3:52 PM, Rob McEwen <rob@???> wrote:
>
> Again, if this feature were implemented - as described - it would be completely innocuous to those didn't go out of their way to implement this. Of course, I would want the implementation by the end user to be very very simple too - but it wouldn't be something that someone could easily mistakenly do, either.
The problem is that with resolver bypass you lose caching, even
when receiving multiple concurrent or closely spaced in time
messages from a legitimate high-volume sender.
The performance impact of this is considerable and undesirable.
As you may know, I am not an Exim developer, so take my opinion for
what it is worth, but IMHO implementing a DNS cache in Exim would not
be a good architectural choice, and without caching the feature is too
costly.
If the incentives on your end are compelling, provide your customers with
a software package that installs a properly configured local resolver for
their use. This will also work with other MTAs and unpatched versions of
Exim.
Your problem seems real enough, and yet your proposed solution may not be
the way forward.
--
Viktor.
