From Deep Sky Technologies:
Denes is an EIMS filter for taking actions on email based on DNS lookups using custom rules and criteria. Denes allows email to be accepted or denied based on DNS lookups, making full support for DNS based blacks lists and white lists available in a single filter; there is even a simple test mode to log DNS lookups without actually denying or accepting email. The most convenient feature of the Denes rules document is that it dynamically reloads after any changes made in it. This means, Denes rules can be added, modified, and/or deleted without having to quit EIMS and launch it again. When any changes to the rules document are detected, Denes will reload the rules for subsequent use in the filter.