Set up Domain-based Message Authentication, Reporting, and Conformance (DMARC) by adding policies to your domain’s DNS records. Policies define how your domain handles suspicious emails. Policies are defined in the form of a TXT record.
There are three possible DMARC policies for how your domain responds to suspicious emails:
- Take no action on the message and log it in the daily report.
- Mark the message as spam and hold it for more processing (quarantine).
- Cancel the message so that it is not sent to the recipient.
Learn more following the below support article from Google G Suite:
https://support.google.com/a/answer/2466580