The document explains how to set the group mode in Quickmail on Moodle to control which groups course participants can email. It describes the three group mode options: No Groups allows emailing all participants, Separate Groups restricts emailing to a participant's own group, and Visible Groups shows all groups but limits emailing to within groups. The steps are to turn on editing, open the Quickmail configuration, select the desired group mode from the dropdown, and save changes.