DMARC is a system that adds some rules for DKIM and SPF, so remote servers have a better idea of what your intention is for messages that fail those 2 systems.
It doesn't really do anything, but adds clarity for actions taken by remote servers, and should lower your spam score in some cases.
Be sure your SPF TXT value contains "-all" (not ~all), and you have DKIM setup before proceeding.
Note: When using the Evolution skin:
- Navigate to "DNS Management"
- Click "Add Record"
- For "Record Type", select "TXT"
- TXT Record Type, seelct "DMARC"
- Enter your email into the "Aggregate Email (RUA)" field: firstname.lastname@example.org
- Click "Add"
For other skins, like "Enhanced", to add a DMARC record, go to your domain's DNS Management, and add the following TXT record:
_dmarc TXT "v=DMARC1; p=none; sp=none; rua=mailto:email@example.com"
Be sure to include the whole thing in "quotes".
The E-Mail Address will sometimes be sent reported spam messages by larger providers. Not all services will email this address, but it's handy if a a client in large email provider clicks "this is spam" for a given message, and you'll be sent that message, so you can determine if someone on your domain is spamming or spoofing, or if the client incorrectly clicked that message (at which point, you'd probably want to remove that client from your mail-out, as they likely don't want it).
The rua=mailto:email portion is not mandatory if you don't want to get these emails.
You can change the values as desired, as per the DMARC specifications:
Google's DMARC guide:
THANKS TO: DIRECTADMIN - DMARC RECORD