Why is DMARC failing when using 'on behalf of' sending, and how can I fix it?

Email marketer from ExpertSender responds by recommending DKIM signing for 'on behalf of' emails to ensure authentication. This allows your domain to vouch for the email's authenticity, even when the 'From' address belongs to another domain.

Email marketer from SendGrid shares that DMARC failures occur when SPF fails to authenticate the sending server for the domain in the 'From' address. Ensure SPF records include the IP addresses of servers sending on behalf of the domain, or use DKIM signing to authenticate the email.

Marketer from Email Geeks shares you need to either support alignment or get an article for your customer base to avoid DMARC enforcement or use your service on a subdomain level (p=reject; sp=none) or simply use your own From: address domain

Email marketer from Mailjet explains that to fix DMARC failures when sending 'on behalf of', you should implement DKIM signing with your own domain. This ensures that even though the 'From' address is the original sender, the DKIM signature verifies that the message came from a legitimate source authorized to send on their behalf.

Email marketer from Reddit explains that for 'on behalf of' sending to pass DMARC, your ESP needs to implement either DKIM signing on your domain or Sender ID. DKIM is the more reliable method, as SPF can be tricky with forwarders.

Email marketer from Postmark responds by recommending using DKIM signing with the sending domain's private key. This allows the receiving server to verify that the message was authorized by the sending domain, even if the 'From' address is different, resolving DMARC alignment issues.

Email marketer from MailerCheck mentions that DMARC failures when using 'on behalf of' sending typically occur because the SPF record doesn't include the IP address of the sending server, or the DKIM signature doesn't align with the 'From' domain. Setting up DKIM properly can resolve this issue.

Email marketer from Email Marketing Forum responds that DMARC failures in 'on behalf of' scenarios typically stem from a mismatch between the 'From' domain and the SPF/DKIM domains. The best solution is to ensure DKIM alignment by signing emails with your own domain's DKIM key.

Email marketer from SparkPost shares that a typical reason for DMARC failure is SPF not authenticating correctly when an email is sent “on behalf of” another domain. To resolve, make sure you have proper SPF records or use DKIM.

Marketer from Email Geeks explains that DMARC fails when SPF and DKIM don't align, either sign with a DKIM for the customer domain or align the return-path/SMTP from with the “header from” so SPF aligns for DMARC to pass. Just adding SPF for the return-path/SMTP from and the mail-from is not enough. The best course of action is to sign DKIM with the customer domain *in addition* to signing with your own DKIM signature (then your SPF setup doesn’t matter, as DKIM will align. And for DMARC to pass it only requires one (SPF or DKIM) to align)

Email marketer from Stack Overflow shares the main issue is DMARC alignment. Either the SPF domain needs to match the From: domain (which it won't in 'on behalf of' sending) or the DKIM signature domain needs to match. Implement DKIM signing correctly.

Expert from Word to the Wise shares that one of the main reasons for DMARC failure is a lack of proper alignment between the From: domain and either the SPF or DKIM domain. When sending on behalf of, the best approach is to implement DKIM signing with your own domain to assert that you are authorized to send on behalf of the 'From:' address.

Expert from Email Geeks explains that it’s easy to get DMARC wrong because it can be so complex. An example of this issue is when there is no DKIM on from domain and SPF doesn’t align, so DMARC failed.

Expert from Spam Resource explains that when sending 'on behalf of', DMARC failures often occur due to SPF failing to authenticate the sending source. To fix this, ensure your SPF record includes all authorized sending sources. However, the preferred method is to implement DKIM with your own domain's signing key, which provides a verifiable link between your domain and the message content, regardless of the 'From' address.

Documentation from RFC Editor describes that DMARC policies are designed to handle cases where email is sent 'on behalf of' a domain. It specifies that either SPF or DKIM must align with the domain in the 'From' header for the message to pass DMARC authentication.

Documentation from AuthSMTP details that 'on behalf of' sending causes DMARC issues because the From address domain doesn't align with the authenticating domain. They advise setting up DKIM signatures correctly so your domain vouches for the message.

Documentation from Microsoft Learn emphasizes that proper SPF and DKIM configuration are crucial for DMARC to pass. When using 'on behalf of', ensure that your sending domain is authorized via SPF and that DKIM signatures use your domain, not the original sender's.

Documentation from Google Workspace Admin Help explains that DMARC relies on alignment between the domain in the 'From' header and the domain used for SPF and DKIM checks. When sending 'on behalf of,' the SPF or DKIM domain may not match the 'From' domain, causing a DMARC failure.

Documentation from DMARC.org details that DMARC has two alignment modes: strict and relaxed. 'On behalf of' sending often fails strict alignment. Relaxed alignment allows subdomain matches, but 'on behalf of' scenarios may still fail if the domains are completely different.