Summary
SPF failures despite correct setup primarily occur due to email forwarding. The recipient server validates the forwarder's IP, which is unlikely in the original SPF record. DKIM is more resilient due to content validation. Mailing lists, autoresponders, Microsoft/Hotmail forwarding, and incorrect SPF syntax also contribute to failures. A small DMARC failure rate can be normal.
Key findings
- Forwarding: Email forwarding is the most common cause of SPF failures.
- DKIM Resilience: DKIM is more resistant to forwarding issues than SPF.
- Mailing Lists/Autoresponders: Mailing lists and autoresponders can trigger SPF failures due to different sending servers.
- Microsoft/Hotmail Forwarding: Microsoft/Hotmail forwarding often causes SPF failures.
- SPF Syntax: Incorrect SPF record syntax contributes to SPF failures.
- Normal DMARC Failure: A small DMARC failure rate can be considered normal.
Key considerations
- Monitor Forwarding: Monitor and understand email forwarding practices.
- Implement DKIM: Implement DKIM to improve authentication and deliverability.
- Review SPF Records: Regularly review and correct SPF record syntax.
- Address MS/Hotmail Delivery: Pay close attention to deliverability to Microsoft/Hotmail addresses.
- Use Authentication Services: Consider using an email authentication service for easier management.
What email marketers say
8 marketer opinions
SPF and DKIM failures can occur despite correct setup primarily due to email forwarding. When an email is forwarded, the recipient server often sees the forwarder's IP address, which is unlikely to be authorized in the original sender's SPF record. This causes SPF checks to fail. Additionally, issues arise from mailing lists, autoresponders, multiple ESPs, and occasionally misconfigured records. DKIM is often more resilient to these issues as it validates the email's content rather than the sending server's IP.
Key opinions
- Email Forwarding: Email forwarding is the primary cause of SPF failures despite correct setup.
- DKIM Resilience: DKIM is generally more resilient to forwarding issues compared to SPF.
- Mailing Lists: Mailing lists often cause SPF failures because the mailing list server becomes the sender.
- Autoresponders: Autoresponders can trigger SPF failures as they originate from different servers.
- Multiple ESPs: Using multiple ESPs without proper configuration can lead to SPF failures.
Key considerations
- Monitor SPF Records: Regularly audit SPF records to ensure they are correctly configured.
- Implement DKIM: Implement DKIM alongside SPF to improve email authentication and deliverability.
- Forwarding Practices: Review email forwarding practices to understand how they might affect SPF results.
- Use DMARC: Implement DMARC to manage how email receivers should handle emails that fail SPF or DKIM checks.
- Consider Authentication Services: Using a service that manages authentication can help with complex configurations.
Marketer view
Email marketer from Email Authentication Blog responds that SPF/DKIM failures happen when email forwarding occurs and the recipient sees the forwarding server's IP. DKIM is less susceptible to forwarding issues because it validates the content of the email, not the sending server.
2 Oct 2021 - Email Authentication Blog
Marketer view
Email marketer from Mailjet shares that SPF failures can occur even with correct setup due to email forwarding, where the forwarder's server IP isn't authorized in the SPF record. Using a service that manages authentication can help.
21 Nov 2021 - Mailjet
What the experts say
3 expert opinions
SPF failures often arise from email forwarding, where the forwarding server's IP isn't in the original SPF record. Microsoft/Hotmail forwarding can be particularly problematic. DKIM can experience random failures due to DNS issues or body modification, and a minor DMARC failure rate is considered normal.
Key opinions
- Forwarding Issues: Email forwarding is a primary cause of SPF failures as the recipient server sees the forwarder's IP.
- Microsoft Forwarding: Microsoft/Hotmail forwarding is known to frequently cause SPF failures.
- DKIM Random Failures: DKIM can experience random failures due to reasons like DNS issues or content modification.
- Normal DMARC Failure Rate: A small DMARC failure rate (e.g., 0.1%) is often considered normal.
Key considerations
- Review Forwarding Practices: Examine email forwarding practices to understand how they impact SPF and DKIM results.
- Monitor Microsoft Delivery: Pay close attention to deliverability when sending to Microsoft addresses due to their forwarding methods.
- Handle DKIM Failures: Understand that DKIM failures can occur randomly and may not always indicate a configuration problem.
- Assess DMARC Reports: Monitor DMARC reports to identify and address potential authentication issues.
Expert view
Expert from Spam Resource, John Levine, explains that SPF failures often occur due to forwarding. When a mail server forwards a message, the recipient server sees the forwarder as the sender. If the forwarder's IP address isn't included in the original sender's SPF record, the SPF check will fail, even if the original setup was correct.
13 Jun 2023 - Spam Resource
Expert view
Expert from Word to the Wise, Laura Atkins, shares that SPF failures are commonly seen when Microsoft (Hotmail) forwards messages. When they forward, the SPF record doesn't always align and often causes SPF fails. She recommends reviewing forwarding practices and authentication methods when sending to Microsoft addresses.
3 Jan 2025 - Word to the Wise
What the documentation says
3 technical articles
SPF failures often occur due to email forwarding. The recipient server identifies the forwarding server as the sender, and if the forwarding server's IP address is not authorized in the original domain's SPF record, the SPF check fails. Other potential causes include incorrect SPF record syntax or exceeding DNS lookup limits.
Key findings
- Forwarding Issues: Email forwarding is a common cause of SPF failures.
- IP Authorization: SPF checks fail if the forwarding server's IP is not authorized in the SPF record of the original sending domain.
- Record Syntax: Incorrect SPF record syntax can lead to SPF failures.
- DNS Lookup Limits: Exceeding DNS lookup limits can result in SPF failures.
Key considerations
- Address Forwarding Issues: Be aware that email forwarding can often lead to SPF failures even with correct setup.
- Correct SPF Syntax: Ensure that SPF record syntax is correct and that all sending server IP addresses are included.
- Avoid Excessive DNS Lookups: Avoid exceeding DNS lookup limits in SPF records.
Technical article
Documentation from Microsoft explains that SPF failures can happen because of incorrect SPF record syntax, exceeding DNS lookup limits, or forwarding. Also, make sure the sending server's IP address is included in the SPF record of the sending domain.
31 Jul 2022 - Microsoft Learn
Technical article
Documentation from dmarcian explains that SPF failures often occur with forwarding because SPF checks the sending server's IP address against the domain's SPF record. When a forwarder sends the email, the recipient sees the forwarder's IP, which is unlikely to be authorized by the original sender's SPF record.
18 Jun 2024 - dmarcian
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