ADP is capable of sending DMARC compliant email because they support custom SPF configurations that achieve DMARC alignment. ADP is an Employee Benefits Platform and is often used by Human Resources teams.
We recommend opening a support ticket to get help with custom SPF configurations as we couldn’t find any relevant ‘how to’ documentation on their site. The most recent support alias we found was: https://www.adp.com/contact-us/customer-service.aspx