SPF is an email authentication method designed to detect and block email spoofing by verifying sender IP addresses against a list of authorized IPs for the domain. For an email to pass SPF alignment under DMARC, the "From" domain (the visible sender) must match the domain used in the SPF check.
Email Forwarding: This is the most common reason for SPF alignment failures. When an email is forwarded, the original sender’s IP address does not match the forwarding server’s IP address. Since the forwarding server is not listed in the original sender's SPF record, the forwarded email fails SPF checks.
Mailing Lists: Similar to forwarding, emails sent to mailing lists and then distributed to list members can fail SPF checks because the mailing list server is not an authorized sender in the SPF record of the original sending domain.
Incorrect SPF Records: Misconfigurations in SPF records can also lead to alignment failures. This includes missing IP addresses or ranges, syntax errors, or not including all legitimate sending sources.
Email forwarding breaks SPF because the mechanism relies on the IP address of the sending server to authenticate the email. Here's how it works:
Initial Send: An email is sent from an authorized sending server.
Forwarding Server: The email is received by a server that then forwards it to another recipient.
Recipient Server: The recipient's server performs an SPF check on the forwarding server's IP address, which is not listed in the original sender’s SPF record, resulting in an SPF failure.
While SPF alignment failures can indicate potential issues, it’s important to note that they are not always indicative of malicious activity. Forwarded emails are legitimate but fail SPF alignment due to the inherent limitations of the SPF protocol in handling forwarded messages.
Implement DMARC with Relaxed Alignment: DMARC allows for strict or relaxed alignment modes. Using relaxed alignment can reduce the number of alignment failures. In relaxed mode, the domain in the "From" address only needs to be a subdomain of the SPF domain, not an exact match.
Use ARC (Authenticated Received Chain): ARC is a newer protocol designed to address issues like forwarding. It allows each entity that handles the email to sign it, creating a chain of custody that can be validated by the final recipient.
DKIM (DomainKeys Identified Mail) Alignment: Ensure that DKIM is correctly configured and aligned. DKIM signatures remain intact during forwarding, making it a robust complement to SPF.
Encourage Direct Delivery: Where possible, encourage senders and recipients to avoid forwarding and instead send emails directly.
SPF alignment failures in your DMARC reports are often due to email forwarding, a common and legitimate practice. Understanding this can help you better interpret your DMARC reports and take appropriate action to ensure email deliverability and security. Implementing DMARC with relaxed alignment, using ARC, and ensuring DKIM alignment can significantly mitigate the impact of SPF alignment failures.
For further assistance on managing SPF alignment issues or any other queries related to DMARC monitoring, please feel free to contact our support team. We're here to help you navigate and optimize your email authentication strategies.
