DMARC operates in the form of a record installed on your domain's DNS that provides policy recommendations for accepting mail from your domain. Policy options are none, monitor, reject, and quarantine. All DMARC policies allow you to provide monitoring addresses. Monitoring addresses will be sent aggregate and forensic reports about all mail sent from your domain. This allows you to monitor who is sending mail from your domain and to ensure that only authorized locations are sending on your behalf. A prime example of this is chase.com. If any unauthorized location tries to impersonate chase.com in email, the message will be rejected and Chase will receive notice of this abuse. This ensures the health of the chase.com domain while also providing evidence of abuse should Chase need to investigate the abuse further.
DMARC was originally created as way to prevent spoofing. Spoofing is the use of a sending domain owned by an outside party. For instance, Yahoo has implements a DMARC rejection policy to prevent abuse of their domain. That means that if you send from a yahoo.com address from your account, the mail be rejected. The only way to send from a yahoo.com address is to do so directly through Yahoo's mail servers.
DMARC can also be an excellent way for organizations to protect their own domain's good reputation. DKIM keys can be used with your ReachMail messages to ensure that mail sent from your account passes your DMARC policy. This allows you to ensure that only authorized locations are allowed to send from your domain.
For any additional questions or concerns, please do not hesitate to contact us at firstname.lastname@example.org.