At Return Path, we have the opportunity to work with some very sophisticated email marketers and I’m very lucky to be working with one in particular. This marketer sends from several domains because they juggle multiple brands across international markets (so you get all the variations of .fr, .de, .be, etc.). When we began collecting data on one of their new domains, our tools detected a strange, recurring issue where their Sender Policy Framework (SPF) authentication was failing. We also saw that when SPF failed, their inbox placement dramatically dropped.
The Impact of a Failing SPF Record
This graph shows what percentage of mail sent was placed in the inbox (vs. spam folder or bounced) for emails sent the week of March 22, 2015. Unfortunately, this graph also ruins the opportunity for me to build up the story to when the SPF issue was resolved on March 25, 2015, as indicated by the inbox placement rate stabilizing around 90%.
Fixing the SPF Record & the Result
When our client tested their SPF records through publicly available online tools, the SPF status on the domain all came back clear. So they asked us, why is Return Path showing that SPF is failing? SPF records describes a list of IP addresses that are allowed to send emails from a specific domain. And this domain was listed.
The answer was that most tools assume that the sending domain (the domain in the from: field) is the same domain in the return-path address. The catch is that mailbox providers check the return-path domain when verifying SPF, and depending on your mail settings, you might have an unfamiliar domain as your return-path domain.
And if you’re curious where SPF is important, see the regional breakdown of inbox placement for an email that had the authentication failure. Since we know that when SPF passed this client’s emails see 90% inbox placement, this is a pretty telling report that shows how important SPF authentication is for European mailbox providers.
Setting Up SPF
For more information about SPF and how to setup SPF records for your domain, visit this step-by-step guide by Dave Langley, Senior Deliverability Consultant.