Implementing DMARC
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.
Prerequisites
Since DMARC relies on DKIM and SPF, first ensure your existing emails are passing these checks:
- DKIM verifies the email wasn’t altered in transit using cryptographic authentication
- SPF authorizes IP addresses to send email for a domain
If you have a verified domain with Sequenzy, your emails are already passing SPF and DKIM.
What is DMARC?
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.
Implementing DMARC
1. Add a TXT _dmarc Record
To start, add a flexible DMARC record to your domain:
| Name | Type | Value |
|---|
_dmarc.example.com | TXT | v=DMARC1; p=none; rua=mailto:dmarcreports@yourdomain.com; |
v - Version: The version of DMARCp - 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.rua - Reporting URI of Aggregate: Provide a valid address that can receive email. The address can be a different domain than the one on which you set the DMARC policy. The aggregate report comes as an email with a .xml file attached that shares the IP sources of your messages and if they passed SPF or DKIM.
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.
2. Test to Confirm Delivery and Passing
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. 3. Upgrade Policy
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.
Reference
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.
| Parameter | Purpose | Example |
|---|
v | Protocol version | v=DMARC1 |
pct | Percentage of messages subjected to filtering | pct=20 |
ruf | Reporting URI for forensic reports | ruf=mailto:authfail@example.com |
rua | Reporting URI of aggregate reports | rua=mailto:aggrep@example.com |
p | Policy for organizational domain | p=quarantine |
sp | Policy for subdomains of the OD | sp=reject |
adkim | Alignment mode for DKIM | adkim=s |
aspf | Alignment mode for SPF | aspf=r |
Why Sequenzy Doesn’t Require DMARC
Sequenzy requires 5 DNS records for domain verification (3 DKIM + 1 SPF + 1 MX), but DMARC is optional. Here’s why:
- DMARC is domain-wide - A DMARC record applies to all email from your domain, not just emails sent through Sequenzy
- You may already have one - Many domains already have a DMARC policy set up
- Configuration varies - The right DMARC policy depends on your organization’s email infrastructure
However, we strongly recommend setting up DMARC for better deliverability and domain protection.
