On 2014-11-13, Heiko Schlittermann <hs@???> wrote:
> Thank you. Reading this it seems to be possible.
> I'll report the solution to this list. (I think, I got this link
> already, but I was confused because the Exchange2013 people kept telling
> me, that it is not possible to reject at RCPT)
it's easy to avoid backscatter, just set errors_to=postmaster@their-domain
that should motivate them to fix their exchange.