[exim] Block mail of reverse DNS fails

Hello,

I hope this is the right place ask and I hope finally I can get a
correct answer. I searched the web, tried several examples but nothing
did the way I expected. Alright let's go to the business:

I have an Exim instance running on Debian Jessie. For each mail that is
received by Exim I would like to check if the reverse DNS for the sender
domain matches the connecting IP and if not reject the mail.

Consider the following scenarios.
* A spammer sends an email from the IP 94.123.123.123 with
info@??? in the "From" field but the domain
spammerwebsite.com doesn't resolve to 94.123.123.123. I want this to be
blocked.
* A spammer sends an email from the IP 94.123.123.123 with
info@??? in the "From" field. In this case example.com is my own
domain and it cannot be located at 94.123.123.123. I want this to be
blocked too.

Please, tell me how to achieve that.

P.S.
* Where can I find the correct documentation?
* How do I debug a configuration file?
* Why can't the configuration start from an empty file?
These are the questions that always pops into my mind while trying to
configure Exim.