# Validate Authenticity

Incoming messages have the ability to be authenticated via the DKIM and DMARC protocols, which are used for ARC signing of messages. The results of these authentication checks are added to an Authentication-Results header which is added to the top of the message. If the most recent Authentication-Results header is from a trusted domain, as specified in the configuration file, the results of both sets of authentication checks are merged. ARC authentication is enable and configured via the `[ARC]` section of `mailman.cfg`. Further documentation is included there.