A broken SPF record means there is some issue in it; either it’s misconfigured, incomplete, or exceeds the technical limits. Such an SPF record fails to perform its responsibility of checking if the email sent from your domain is authenticated. This may also disrupt the flow of legitimate emails from your domain, leaving security gaps and making your domain vulnerable to phishing, spoofing, ransomware, and other abuses.
This blog shares what causes a broken SPF record and how you can fix it.
Implications of a broken SPF record
Neglecting a broken SPF record can cause you more harm than you think. Here’s all that can possibly happen if you don’t fix it at the earliest-
1. Failed authentication
If your SPF record is broken, email servers won’t be able to properly authenticate emails sent from your domain. This way, even illegitimate and potentially malicious emails will pass through. Emails that don’t pass the SPF check are either placed in the spam/ junk folder or rejected by receiving servers; neither of these actions is right for a legitimate email falsely accused of being illegitimate because of a broken SPF record. If critical transactional or marketing emails fail to reach customers, your business reputation will take a toll and might even lead to financial losses.
2. Vulnerability to email phishing and spoofing
Threat actors are always on the lookout for broken SPF records so that they can send phishing and spoofing emails without getting flagged. Also, frequent misuse of your domain for spam and phishing leads to blocklisting by email providers, severely impacting email deliverability for legitimate messages.
3. DMARC and SPF dependence
DMARC builds on SPF and DKIM results. For DMARC to pass, the domain in the email’s SPF result must match the ‘From’ header. A broken SPF record can break this alignment, causing DMARC failures. So, if your DMARC record is set to a ‘quarantine’ or ‘reject’ policy, messages that fail SPF checks because of the broken record will be marked as spam or blocked.
4. Reporting and monitoring issues
SPF errors appear in DMARC aggregate reports as ‘permerror’ or ‘fail,’ indicating that the SPF check couldn’t complete due to misconfigurations. If this happens frequently, the performance of your emails will be obscured, and there will be instances of false positives and negatives.
What causes a broken SPF record, and how can each of these be fixed?
Here are the typical reasons that make an SPF record erroneous.
1. Syntax errors
An SPF record is a structured DNS entry; any typographical or formatting mistakes render it invalid. Common issues that trigger it are-
- Missing spaces or colons.
- Incorrect tags or unsupported mechanisms.
- Misplaced modifiers like ~all, -all, or +all.
Impact
The receiving mail servers are not able to parse your SPF record. This results in failed SPF checks, causing emails to be flagged as spam or rejected.
Solution
There are many SPF lookup tools online. Just run your record through one of them; it will show you the errors that you can fix before publishing it.
2. Too many DNS lookups
SPF relies on DNS lookups for mechanisms like include, a, mx, ptr, and redirect. However, as per the RFC specifications, there is a lookup limit of 10 per record. So, if your record has exceeded this limit, the SPF checks will fail with a ‘permerror.’ This means that legitimate emails may be marked as spam or get rejected. For example, if an SPF record includes multiple third-party services, like email marketing platforms, each ‘include’ mechanism will be counted towards the lookup limit of 10.
Solution
- Consolidate IP addresses to minimize lookups.
- Use tools to flatten SPF records by pre-resolving DNS lookups. Check out our automatic SPF flattening tool.
- Regularly audit third-party services included in your SPF record.
3. Multiple SPF records
Each domain should have only one SPF record corresponding to it. Multiple SPF records for the same domain cause a conflict between mechanisms because DNS servers fail to determine which record they should refer to for your emails.
Solution
Merge multiple SPF records into one. Review your DNS settings to identify all SPF records associated with your domain. Then, consolidate all valid mechanisms into one record. Ensure there are no redundancies and that the record doesn’t exceed the lookup limit of 10.
4. Improper use of wild cards
Wildcards can simplify SPF records but must be used carefully. Improper use can invalidate the record or create security risks. For example, if you add a ‘*’ mechanism, then you are broadly allowing all domains to send emails on your behalf. This authorizes even the potentially malicious sources, opening avenues for threat actors.
Solution
Avoid unnecessary wildcards and stick to explicitly defined mechanisms and IPs.
5. DNS configuration issues
SPF records depend on accurate DNS configuration, and any issues in DNS hosting can disrupt their functionality. Common problems include deletion of SPF records, incomplete propagation across DNS servers, and misconfigured DNS zones or syntax errors during updates. These errors prevent receiving servers from retrieving the SPF record, causing authentication failures. This can lead to emails being flagged as spam or rejected entirely, impacting email deliverability and domain credibility.
Solution
- Monitor DNS changes carefully.
- Use DNS management tools to validate the accuracy of SPF records after updates.
- Ensure proper propagation by verifying the record using DNS query tools.
6. Overly broad mechanisms
Using mechanisms like +all allows any mail server to send emails on behalf of your domain. This completely undermines the purpose of deploying SPF in the first place.
Solution
Always end your SPF record with ~all or -all to enforce strict validation.
- ~all: Soft fail, allowing testing and adjustments.
- -all: Hard fail, blocking unauthorized senders entirely.
Final words
A broken SPF record is a vulnerability that threat actors can exploit to send phishing and spoofing emails from your domain. Such emails will not be authenticated and are delivered as usual. So, always keep your SPF record updated and ensure there is only one for your domain. If your SPF record exceeds the lookup limit, contact us. We will help you bring it under the limit.
