It’s common for legitimate emails to be falsely marked as spam or rejected because they failed the SPF verification checks. While this is not a one-off occurrence, it does leave room for missed conversations, which can lead to reputational and financial damages. SPF is a strong tool against phishing and spoofing emails sent from your domain, but in some scenarios, genuine emails might not be placed in the recipients’ mailboxes.
This blog shares what these scenarios are and how to manage them to avoid unintended consequences.

Possible reasons for false positives in SPF
Incomplete SPF records
If your domain’s SPF record doesn’t list all the authorized servers, genuine emails sent by you will be flagged. So, ensure that you make a holistic list of all the IPs and servers allowed to be used to send emails on behalf of your brand. Then, whenever you introduce a new IP or server for your business, add it to your SPF record.
Dynamic IP addresses or third-party services
Emails from dynamic IPs that are not listed in the SPF record may be treated as unauthorized. Similarly, emails sent through third-party services can be flagged if their IPs are not properly included in the SPF record. Additionally, if the SPF lookup limit of 10 is exceeded, some valid entries might be skipped, causing legitimate emails to fail authentication.

Email forwarding
When an email is forwarded, the forwarder’s server often resends the email using its own IP address instead of the original sender’s IP. During SPF verification, the recipient’s mail server checks whether the forwarder’s IP is authorized in the SPF record of the original sender’s domain. Since the forwarder’s IP is usually not included in the original sender’s SPF record, the SPF check fails, causing the email to be flagged as unauthorized, even though it was forwarded legitimately.
Changes in infrastructure
If you have switched to a new email service provider or added/removed mail servers and your SPF record is not updated, some legitimate emails may be marked as spam or bounce back.
Misconfigured SPF records
If you haven’t used the right syntax in your DNS SPF record or it has spelling errors, there will be chances of false positives. To avoid this, frequently run your SPF record through a lookup tool to learn and fix the issues before they become exploitable vulnerabilities.
Overcoming SPF’s shortcomings with DMARC
When you implement SPF with DKIM and DMARC, your domain’s security posture improves. DMARC helps overcome SPF’s shortcomings with its reporting feature that sends domain owners feedback reports on how their emails are authenticated. It also helps with email forwarding issues where SPF usually falls short.

With DMARC, domain owners set the rules for handling such emails. Using DMARC to address SPF’s shortcomings improves email security by offering alignment and reporting features to combat spoofing and phishing.
DMARC ensures that the ‘From’ domain matches the domain authenticated by SPF or DKIM. Moreover, DMARC lets domain owners tell receiving servers how to handle emails that fail SPF or DKIM checks, allowing for more customized and effective email authentication. This prevents email-based phishing and spoofing.