SpamAssassin Plugin: DKIM
DomainKeys Identified Mail (DKIM) is a method by which emails are signed by the organisation responsible for the senders domain and are placed in the DKIM-Signature: header field.
The DKIM module is activated by default on 3.3 installs. Otherwise the following can be added to local.pre
Generated documentation for the DKIM plugin: v 3.3.x