Sender Policy Framework (SPF) is an email authentication mechanism used by domain owners and organizations to review emails sent by other companies to tackle phishing attempts on their domains. However, these records can be configured incorrectly due to their complex nature, resulting in validation errors such as "SPF validation failed". A scenario like this can be time-consuming and costly for the company. In this article, we explain why an SPF validation error occurs and how they can be fixed.
SPF Validation Error
If the Sender Policy Framework (SPF) validation fails for a sender's domain, an SPF validation error can occur. Records in SPF format must be well-formed. However, even well-formed SPF records can occasionally generate warnings stating that the SPF information is configured incorrectly.
Top 10 Causes of SPF Validation Errors
- Multiple SPF records: Each domain should have only one SPF record for each SPF version. Users should never add a new record next to an existing one, rather update old records.
- SPF validation not available: SPF validation may not be available because there is no SPF record for the domain.
- Too many DNS lookups: Users can only perform 10 nested DNS lookups at a time. If you exceed this limit, the SPF check will fail.
- Syntax error: SPF record must be structured correctly. It must start with the tag ‘v = spf1’ and end with the tag ‘all’. Both tags need to be used only once in an SPF entry.
- Using the PTR mechanism: PTR is an obsolete technique and when used, senders can ignore SPF entries.
- Unknown parts: Content that is not part of the SPF standard may have been inserted.
- Invalid macros: SPF macro settings may be incorrect.
- No record termination: The standard backup mechanisms for SPF records should be ‘all’ methods or ‘redirect’ modifiers.
- Multiple backup scenarios: There should only be one backup option in SPF records.
- DNS type ‘SPF’ use: RFC 7208 made the DNS ‘SPF’ (/ 99) obsolete. DNS TXT resource records (type 16) must be used to publish SPF records.
Meaning of "Error SPF Validation Failed Mode Normal"
Emails sent by marketers may bounce back for a variety of reasons. When the validation fails, those sending the email may get a "554 Denied Mode Normal" SMTP error from the remote mail server. The most common cause of a "554 Denied" issue is faulty reverse DNS or greylisting.
Error Greylisted emails are referred to as postponed in messages. Greylisting is a spam-prevention technique used by mail servers. Consider the case where a sender isn't on a whitelist and the receiving server employs greylisting. In that scenario, the receiving server temporarily rejects the message, and a bounce back-like return message is produced with the temporary fault mentioned. Senders should, therefore, ask receivers to add them to their whitelist to avoid getting greylisted.
SPF verification problems may arise, and the SPF record may need to be updated. To do reverse DNS lookups, MX records must be linked with a record that has a PTR record. If forwarding services are utilized, forward IPs should also be added to the SPF1 record. Moreover, a valid record can be generated using an online SPF generator.
As demonstrated above, SPF validation failure notifications might be issued for a variety of reasons. Configuring SPF records correctly and avoiding common mistakes may significantly improve email deliverability rates and reduce spam. To check your SPF record, use EmailAuth’s free SPF checker tool.
Original source: https://www.reddit.com/user/emailauth-io/comments/qg1c2q/spf_validation_errors_and_how_to_troubleshoot_them/
Published by nimisha rawat