Why is Google Postmaster Tools showing authentication failures despite SPF being set up?
Summary
What email marketers say11Marketer opinions
Email marketer from Quora explains that Google Postmaster Tools reporting failed SPF record indicates your SPF record contains errors. Recommends that you check the syntax of the SPF record using online SPF checkers.
Email marketer from Email Discussions highlights that having multiple SPF records for a single domain is invalid and can cause unpredictable results. They advise consolidating all SPF mechanisms into a single SPF record.
Email marketer from StackOverflow explains that if you are using multiple includes in your SPF records, some DNS servers might not be able to handle the number of lookups which will cause your SPF record to fail.
Email marketer from Reddit's r/emailmarketing notes that even with SPF passing, the 'header from' domain not matching the 'envelope from' domain can cause issues, as DMARC requires SPF alignment for full authentication. They suggest ensuring these domains align for optimal results.
Marketer from Email Geeks mentions that Google Postmaster Tools data reporting regularly lags behind and that zeros are common. Problems arise when the data is in between.
Marketer from Email Geeks shares that they are also seeing authentication failures in Google Postmaster Tools even though the customer has SPF set up, noting the issue seems to have started on the 19th.
Email marketer from CPanel forums recommends using a tool such as mail-tester.com to test your SPF record is configured correctly.
Email marketer from WebHostingTalk forums says that if you are sending email from subdomains, you need to ensure that an SPF record for the subdomain is also set up, and not just for the primary domain.
Email marketer from StackExchange suggests the issue could be with the Return-Path domain SPF record as this needs to match the from domain. They suggest checking this.
Email marketer from MXToolbox Forum suggests using a tool such as MXToolbox to diagnose your SPF record. It could be invalid due to a typo.
Email marketer from Reddit's r/emailmarketing explains that SPF records might not be correctly configured if they exceed the DNS lookup limit (more than 10 lookups). This can lead to SPF failing, even if a record exists.
What the experts say2Expert opinions
Expert from Word to the Wise explains that Google Postmaster Tools might show SPF failures in forwarding scenarios. The IP authenticating needs to be the original sender and needs to authenticate at the initial sending and the forward.
Expert from Spam Resource responds that although your SPF record may be technically correct, the 'HELO' domain (the domain presented by the sending server during the SMTP handshake) may not be included in the SPF record. Some receiving mail servers perform SPF checks on the HELO domain, not just the MAIL FROM domain.
What the documentation says5Technical articles
Documentation from EasyDMARC explains that SPF fails if the sending server's IP address is not listed in the SPF record as an authorized sender.
Documentation from Google Workspace Admin Help explains that if your SPF records exceed the 10 DNS lookup limit, it will cause SPF to fail and they suggest flattening your SPF records.
Documentation from dmarcian explains that a 'permerror' in SPF typically means there's a permanent error with the SPF record itself, such as syntax errors, exceeding the character limit, or exceeding the number of DNS lookups. They recommend checking the record for errors and ensuring it's correctly formatted.
Documentation from RFC explains that an SPF record should not cause more than 10 DNS lookups. The SPF evaluation MUST be terminated with a "permerror" if the number of mechanisms and modifiers that cause DNS lookups exceeds this limit
Documentation from Microsoft Learn explains that DNS propagation issues can sometimes cause SPF checks to fail temporarily. If a new SPF record has been created, it may take some time for the changes to propagate across the internet.