How does email forwarding affect SPF, DKIM, and DMARC validation?

Email marketer from Reddit explains that if forwarding breaks both SPF and DKIM, DMARC will likely fail, potentially causing emails to be rejected or marked as spam, depending on the DMARC policy set by the sending domain.

Email marketer from StackOverflow highlights that SPF fails upon forwarding because the IP address of the forwarding server differs from the IP authorized by the original domain's SPF record. The email now originates from a server not permitted by the sender's SPF policy.

Marketer from Email Geeks explains that if DKIM fails, that can happen if the message body is changed when forwarded.

Marketer from Email Geeks explains that DMARC only needs aligned SPF or DKIM to pass, and forwarding can break SPF and/or DKIM depending on how it's done.

Email marketer from Mailhardener explains that forwarding of emails is a major cause of DMARC failures. When an email is forwarded, the source IP address changes, causing SPF to fail. If DKIM also fails because the message content is altered during forwarding, DMARC will fail as well.

Marketer from Email Geeks suggests that if there are no bounces and only data from aggregate reports, it could be DMARC working as expected and those are spoofing attempts.

Marketer from Email Geeks explains it may be reporting SPF failure, or SPF alignment failure, stating that forwarding breaks SPF, but if DKIM passes and aligns, you're still DMARC-compliant.

Email marketer from Email on Acid shares that when an email is forwarded, the SPF record is unlikely to pass because the sender's IP will not match the original sending server. If the DKIM signature also fails, the email will fail DMARC authentication.

Email marketer from cPanel Forum responds that when an email is forwarded, the IP address of the sender will be different. The email will originate from the new mail server doing the forwarding. Because of the new IP, the SPF record will no longer match. If the email fails both SPF and DKIM, then it will fail the DMARC check as well.

Marketer from Email Geeks doesn't know if MS honors the reject policy request or not, but they shouldn't for messages where they're breaking both SPF and DKIM.

Email marketer from SuperOffice shares that SPF records can fail on forwarded emails because the forwarding server's IP address is different from the IP address authorized in the SPF record of the sending domain. This can lead to DMARC failures.

Email marketer from EmailVendorSelection explains that forwarding can cause emails to fail DMARC checks because SPF relies on the IP address, which changes during forwarding. If DKIM isn't properly implemented or is also broken during forwarding, DMARC will fail. This can affect email deliverability.

Expert from Word to the Wise shares information about Authenticated Received Chain (ARC), explaining that ARC preserves email authentication results across multiple hops. ARC helps maintain authentication when forwarding occurs and helps solve issues forwarding causes with SPF, DKIM, and DMARC.

Expert from SpamResource explains that SPF failures in forwarded emails are due to the receiving mail server checking the IP address against the SPF record of the original sender. When an email is forwarded, the IP address of the forwarding server is used, which does not match the authorized IPs in the SPF record, causing a failure.

Documentation from Google explains that forwarding can disrupt SPF and DKIM authentication. Because forwarded messages come from a different server, SPF checks might fail. If the forwarding process alters the message content, DKIM could also fail, potentially causing the messages to be flagged as spam.

Documentation from RFC Editor explains that standard email forwarding is incompatible with SPF. SPF authenticates the sender based on the IP address of the sending server, which changes when an email is forwarded to a different server.

Documentation from AuthSMTP explains that DKIM signatures can be broken by forwarding if the forwarding server modifies the email content. Changes such as adding disclaimers or converting the message to plain text will invalidate the DKIM signature.

Documentation from dmarc.org explains that forwarding can break DMARC authentication as it often invalidates SPF and sometimes DKIM, leading to potential delivery issues. DMARC relies on the alignment of SPF and DKIM with the From: domain to ensure legitimate emails are delivered.

Documentation from Microsoft Learn explains that SPF validation fails when an email is forwarded because the sending server's IP address no longer matches the authorized IP addresses listed in the SPF record of the original sending domain. The forwarded email appears to be coming from an unauthorized source.