DMARC stands for Domain-based Message Authentication, Reporting, and Conformance
It can be used as a way to prevent specific type of SPAM. Hence it should be added as TXT record in your DNS zone, just like SPF and DKIM signatures.
Example DMARC policies
These are some example policies and how they appear in the DNS TXT record.
The values in these examples are defined in DMARC TXT record values, below.
|Actions to take for failed DMARC check||TXT record contents|
|Take no action on messages that fail the DMARC check. Email a daily report to [email protected]|
|Put 5% of the messages that fail the DMARC check in recipients’ spam folders. Email a daily report to [email protected]|
|Reject 100% of messages that fail the DMARC check. Email a daily report to two addresses: [email protected] and [email protected] Failed messages cause an SMTP bounce to the sender.|