[exim] Blocking hosts without MX/A records in DNS

Hi, list!

In order to try to reduce the (huge!) quantity of daily spam, we want to
reject the E-Mails coming from domains which do NOT have a valid MX or
A record (aka: the domain does not exist, or is not fully configured).

I thought, verify = sender do that, but it doesn't... :(
How can I implement this check? I use Exim 4.62.

Thanks a lot for your help!
--
_______________________________
Luca Bertoncello
-Programmierung / Mailserver-

IMS Internet-Media-Service GmbH
Bayrische Str. 18
01069 Dresden

Fon: +49 351 2112034
Fax: +49 351 2112020
E-Mail: bertoncello@???