DMARC helps protect your domain from being used in phishing attacks and improves email deliverability by giving mailbox providers confidence that your emails are legitimate.
DMARC (Domain-based Message Authentication, Reporting, and Conformance) is an email authentication protocol that instructs mail servers what to do if an email message fails SPF and DKIM, preventing email spoofing (forged headers). DMARC is added to a domain through a TXT record at _dmarc.By preventing spoofing, a domain can build trust with mailbox providers, as it allows them to verify that emails are authorized to send on behalf of that domain.An email must pass either SPF or DKIM checks (but not necessarily both) to achieve DMARC compliance and be considered authenticated. A message fails DMARC if both SPF and DKIM fail.
To start, add a flexible DMARC record to your domain:
Name
Type
Value
_dmarc.example.com
TXT
v=DMARC1; p=none;
This record specifies a few parameters (see Reference section for more details):
v - Version: The version of DMARC
p - Policy: Tells the inbox how to process messages that fail DMARC. Options are none, quarantine, reject. It’s best practice to use quarantine or reject, but only do so once you know your messages are delivering and fully passing DMARC.
Once you’ve added a basic record, you should set up DMARC reporting to monitor your results.
To ensure you don’t accidentally introduce breaking changes to your email
sending, we suggest starting with a policy of p=none; before moving to a
stricter policy.
To test emails, send an email from all the applications and services your domain uses. Confirm that the messages are delivered to the inbox and that the headers show DMARC passing.Spend a few days at this step to ensure you’re checking all sources of email from your domain and catch email that is sent at a different cadence than daily.To confirm DMARC passed, you can inspect the email headers and confirm there is dmarc=pass.
Gradually identify email sources using tools like Google Postmaster
Tools, which provides DKIM/SPF feedback.
DMARC monitoring
services can aggregate
your email sources by collecting DMARC reports, helping you discover any
services sending email on your domain’s behalf.
Once you have verified DMARC is passing across all your sending, you should upgrade your policy to p=quarantine;. This policy gives mailbox providers greater confidence in your domain since your domain only allows authenticated email.
Policy
Description
p=none;
Allow all email. Monitoring for DMARC failures only.
p=quarantine;
Send messages that fail DMARC to the spam folder
p=reject;
Bounce delivery of emails that fail DMARC
Once your policy is p=quarantine; or p=reject;, you can explore setting up
BIMI (Brand Indicators for Message Identification), which can provide
established brands even greater sending credibility by displaying a logo as an
avatar in an email client.
DMARC includes a reporting mechanism via the rua parameter, which tells mailbox providers where to send aggregate reports about emails from your domain. These reports are XML files that show which IP addresses are sending email on your behalf and whether those emails pass SPF and DKIM.
Raw DMARC reports are XML files sent as email attachments — they’re not meant to be read directly. To get value from DMARC reporting, you should use a free monitoring service that parses these reports into a readable dashboard.
Don’t point rua at your own email address (e.g., dmarc@yourdomain.com). You’ll receive raw XML files that are difficult to interpret without specialized tooling.
Reports typically arrive daily. Give it a week or two to collect enough data before making policy decisions.
While the DMARC protocol includes both pct and ruf parameters, they are
not widely followed by mailbox providers. These settings may not be respected
or followed.
