In email marketing, DMARC (Domain-based Message Authentication, Reporting and Conformance) is an email authentication protocol that helps protect your domain from being used in phishing attacks, spoofing, and other fraudulent email activities. DMARC builds on two other authentication methods—SPF and DKIM—and tells receiving mail servers what to do when an email fails authentication checks.
DMARC works by verifying that emails claiming to be from your domain are actually authorised by you. If an email fails the check, DMARC instructs the recipient’s server how to handle it: deliver it anyway, quarantine it (send to spam), or reject it outright.
For example, if a scammer tries to send a phishing email pretending to be from yourcompany.com, DMARC can prevent that email from reaching inboxes by instructing servers to reject messages that don’t pass authentication.
Why DMARC matters for email marketers
DMARC is no longer optional—it’s a critical part of email marketing best practices and deliverability. Major mailbox providers like Gmail, Yahoo, and Outlook now require or strongly recommend DMARC for bulk senders.
Without DMARC, you risk:
- Lower inbox placement – Emails may be filtered to spam or blocked entirely
- Domain spoofing – Bad actors can impersonate your brand, damaging trust and reputation
- Deliverability issues – Providers treat unauthenticated senders as higher risk
- Loss of customer trust – If scammers use your domain, recipients may lose confidence in your legitimate emails
Setting up DMARC is essential for protecting your brand, maintaining sender reputation, and ensuring your emails reach subscribers’ inboxes. It’s one of the most important technical steps you can take to improve deliverability and safeguard your audience.
How DMARC works
DMARC relies on two foundational email authentication protocols: SPF and DKIM.
SPF (Sender Policy Framework)
SPF verifies that the server sending your email is authorised to send on behalf of your domain. It works by checking the sending server’s IP address against a list of approved IPs published in your domain’s DNS records.
DKIM (DomainKeys Identified Mail)
DKIM adds a digital signature to your emails, proving they haven’t been tampered with in transit. The receiving server checks this signature against a public key published in your DNS.
DMARC ties them together
DMARC checks whether an email passes SPF or DKIM (or both), and whether the domain in the “From” address aligns with the domain that passed authentication. If the checks fail, DMARC tells the receiving server what to do based on your policy.
DMARC also provides reporting, so you can see who’s sending email on behalf of your domain and whether those messages are passing or failing authentication.
Why DMARC is now required for email marketers
In 2024, major mailbox providers introduced stricter authentication requirements for bulk senders. Gmail and Yahoo both now require:
- SPF and DKIM authentication
- DMARC policy published on your sending domain
- Low spam complaint rates
- Easy unsubscribe options
These requirements apply to anyone sending more than 5,000 emails per day to Gmail addresses (and similar thresholds for other providers). But even if you send less, implementing DMARC is still a best practice.
DMARC is no longer just about security—it’s about deliverability. Providers use authentication as a signal of sender quality. Authenticated emails are more likely to reach the inbox, while unauthenticated emails face higher scrutiny and filtering.
Common DMARC mistakes
DMARC setup is technical, and small errors can cause deliverability issues.
Not aligning domains
DMARC requires alignment between the “From” domain and the domain that passes SPF or DKIM. If you send from newsletter@yourbrand.com but authenticate using a subdomain like mail.yourbrand.com, alignment may fail. Check your ESP’s documentation for guidance.
Skipping monitoring
Starting with strict policies without monitoring can block legitimate email. It’s important to review authentication reports before tightening your policy.
Forgetting about third-party senders
If you use multiple email platforms (marketing automation, transactional email, CRM tools), make sure all are properly authenticated and aligned. Unauthorised senders will fail DMARC checks.
Ignoring reports
DMARC reports show you what’s working and what’s not. Ignoring them means missing critical insights about your email authentication and potential spoofing attempts.
Not updating DNS records
If you switch email providers or change sending infrastructure, update your SPF, DKIM, and DMARC records accordingly.
Benefits of implementing DMARC
Setting up DMARC takes effort, but the benefits are significant.
- Better deliverability – Authenticated emails are trusted by mailbox providers and more likely to reach the inbox.
- Brand protection – DMARC prevents scammers from impersonating your domain, protecting your reputation and your subscribers.
- Visibility and control – Reports show you exactly who’s sending email on behalf of your domain and whether it’s passing authentication.
- Compliance with provider requirements – Meeting Gmail and Yahoo’s authentication standards keeps you in good standing with major inbox providers.
- Increased subscriber trust – When recipients know your emails are legitimate, they’re more likely to engage.
DMARC and email service providers
Most reputable email service providers (ESPs) support DMARC and can guide you through setup. Many will:
- Provide SPF and DKIM records for you to add to your DNS
- Offer DMARC setup instructions or support
- Handle domain alignment automatically
- Provide dashboards or tools to monitor authentication status
If your ESP doesn’t support DMARC or makes it difficult to implement, it may be time to consider switching to a platform that prioritises deliverability and best practices.
Key takeaway
DMARC is an essential email authentication protocol that protects your domain from spoofing, improves deliverability, and builds trust with subscribers. As part of email marketing best practices, implementing DMARC—along with SPF and DKIM—is no longer optional. It’s a critical step to ensure your emails reach the inbox and your brand stays secure.