What causes DMARC bounces and SendGrid authentication issues?
Summary
What email marketers say9Marketer opinions
Email marketer from Email Marketing Tips shares that incorrect DNS settings can cause DMARC failures. If DMARC, SPF, or DKIM records are not correctly configured in your DNS settings, email authentication will fail. This can result in emails being rejected or marked as spam.
Email marketer from Mailhardener Blog explains that DMARC bounces can occur if you have a 'reject' policy and emails fail authentication. They also point out that incorrectly configured DMARC reporting can lead to confusion, as you might receive bounce notifications for legitimate emails that are being rejected due to DMARC policies at the recipient's end.
Email marketer from Reddit shares that one common issue with SendGrid and DMARC is related to shared IP addresses. If other users on the same shared IP are sending spam, it can negatively impact your reputation and lead to DMARC failures, even if your own emails are properly authenticated.
Marketer from Email Geeks confirms that the SendGrid issue was resolved, including a link to the SendGrid status page.
Email marketer from Email Marketing Forum explains that email forwarding can cause DMARC failures. Forwarding breaks SPF authentication because the original sender's IP address no longer matches the SPF record. DMARC policies may then cause issues for forwarded emails.
Marketer from Email Geeks confirms that they can see a SendGrid domain in the DKIM header, leading to a DMARC failure in some cases.
Email marketer from Email Deliverability Forums explains that when using SendGrid, failing to properly configure reverse DNS (rDNS) for your dedicated IPs can affect deliverability and cause DMARC failures. rDNS helps recipient servers verify that the IP address is associated with your domain.
Email marketer from StackOverflow explains that issues can occur when SendGrid's dedicated IPs are not properly warmed up. Sending high volumes of email without warming up the IP can result in poor reputation and DMARC failures because recipient servers view the sudden volume as suspicious.
Marketer from Email Geeks suggests that the original poster check the email headers and that they might find SendGrid domains in the authentication headers instead of their own.
What the experts say3Expert opinions
Expert from Email Geeks shares that he would expect DMARC bounces to be specific to a particular sending domain or a particular receiving mailbox provider.
Expert from SpamResource explains that one cause of DMARC failure is improper handling of subdomains. If you have a DMARC policy set for your main domain, it also applies to subdomains unless you explicitly define a different policy for the subdomain. This can cause issues if the subdomains are not properly configured to send authenticated email.
Expert from Word to the Wise explains a situation that could trigger DMARC failures is when an account is targeted for list bombing. List bombing is where bots subscribe a victim email address to many different lists and then email authentication may fail and be rejected due to the increase in mail volume and changes in sending patterns.
What the documentation says5Technical articles
Documentation from RFC explains that if the domain in the 'From:' header does not align with the domain used in the SPF or DKIM authentication, it will lead to a DMARC failure. DMARC requires alignment between the visible 'From:' domain and the authenticated domain.
Documentation from Google Workspace explains that an improperly configured SPF record can lead to DMARC failures. Common misconfigurations include missing the 'include:' mechanism for third-party senders (like SendGrid), exceeding the DNS lookup limit, or having syntax errors in the SPF record.
Documentation from SendGrid explains that incorrect DKIM configuration is a common cause of authentication failures. This includes issues like incorrect DNS records, mismatched selectors, or problems with the signing process itself. When DKIM fails, DMARC can also fail if the other alignment requirements aren't met.
Documentation from DMARC.org explains that DMARC failures often stem from SPF and DKIM alignment issues. If SPF fails to authenticate the sender's IP address or DKIM signatures are invalid or missing, DMARC policies (especially 'reject' or 'quarantine') will cause bounces or emails to be marked as spam.
Documentation from Microsoft explains that a common cause of DMARC failure is that authentication fails due to modifications to the email content in transit. Some email systems modify email content or add footers/signatures, breaking DKIM signatures.