A DMARC policy allows a sender to indicate that their emails are protected by SPF and/or DKIM, and give instruction if neither of those authentication methods passes. Please be sure you have a DKIM and SPF set before using DMARC.
You do not have a DMARC record, please add a TXT record to your domain _dmarc.DOM.TLD with the following value:
v=DMARC1; p=none