Blackboard Connect supports DMARC compliance via SPF and DKIM.
To configure DKIM, see this article: https://help.blackboard.com/Community_Engagement/Administrator/Community_Settings/District_and_School_Settings/Manage_Global_Settings_for_All_Organizations/Improve_Email_Delivery
To configure SPF, see this article: https://help.blackboard.com/Community_Engagement/Administrator/Community_Settings/District_and_School_Settings/Manage_Global_Settings_for_All_Organizations/Improve_Email_Delivery