How can I resolve DMARC verification failures when using a subdomain for email sending?
Summary
What email marketers say10Marketer opinions
Email marketer from Postmark shares that properly warming up the IP address associated with the subdomain is essential for deliverability. Sending low volumes initially and gradually increasing it helps build a positive sender reputation.
Email marketer from Valimail shares that a common cause of DMARC failures is misconfigured DNS records for the subdomain, particularly SPF and DKIM. It's crucial to ensure these records are correctly set up and validated.
Email marketer from EasyDMARC responds that implementing a 'relaxed' SPF mode can sometimes cause DMARC failures on subdomains. It recommends using 'strict' SPF alignment where possible for better security and compliance.
Email marketer from EmailToolTester shares that using online tools to simulate email sending and check DMARC/SPF/DKIM results is a good way to test the configuration before going live.
Email marketer from Reddit User u/mailauthguy shares that exceeding the SPF record lookup limit (10 DNS lookups) can cause SPF failures, which in turn affects DMARC. This is more likely to occur with subdomains if they include many third-party services.
Email marketer from AuthSMTP explains that after making changes to DNS records (SPF, DKIM, DMARC) for the subdomain, it's important to check that these changes have propagated globally before sending email.
Marketer from Email Geeks suggests creating a separate DMARC record for the subdomain with a policy of 'none' during testing to resolve bounce issues.
Email marketer from MXToolbox responds that using their DMARC record lookup tool can help identify issues with the subdomain's DMARC record, such as syntax errors or incorrect policy settings.
Email marketer from Mailjet shares that ensuring DKIM alignment (where the 'd' tag in the DKIM signature matches the domain used in the 'From' address) is critical for DMARC to pass. Misalignment is a common cause of failures.
Email marketer from StackOverflow User TechGuru123 shares that email forwarding can break SPF authentication, leading to DMARC failures, especially if the subdomain is used for transactional emails that are often forwarded.
What the experts say3Expert opinions
Expert from Word to the Wise shares that testing your configuration is key. Send a test email to an address you control and check the headers to see if DMARC passes. Repeat this after any changes.
Expert from Spamresource.com responds that a common issue for subdomain DMARC failures is simply a misconfigured record. They recommend double-checking the syntax, policy settings, and DNS propagation.
Expert from Spamresource.com suggests to check your DMARC record using an online analyzer. These tools can identify syntax errors and configuration issues that lead to verification failures with subdomains.
What the documentation says5Technical articles
Documentation from DMARC.org specifies that subdomains inherit the parent domain's DMARC policy unless a specific subdomain policy is defined. Failure to define a policy can lead to unexpected results.
Documentation from Amazon Web Services explains that when using Amazon SES for sending emails from a subdomain, proper configuration of SPF, DKIM, and DMARC is necessary to ensure deliverability and avoid DMARC failures.
Documentation from Google Workspace Admin Help explains that DMARC policies are inherited by subdomains. If a subdomain needs a different policy, a specific DMARC record must be created for that subdomain.
Documentation from Microsoft Learn explains that if using Exchange Online Protection (EOP), it's crucial to configure DMARC correctly for subdomains to prevent spoofing and phishing attacks.
Documentation from RFC 7489 explains that setting up DMARC reporting (both aggregate and forensic) for the subdomain allows for monitoring authentication results and identifying potential issues causing failures.