Sender Policy Framework (SPF) Failure: Understanding Different Types and Causes
In today’s digital age, email is a critical communication tool used by individuals and organizations around the world. To ensure the authenticity of emails and prevent malicious attacks, email authentication protocols, such as Sender Policy Framework (SPF), have been developed.
SPF is a DNS-based email authentication protocol that helps to prevent email spoofing by verifying that the domain name listed in the “From” field of an email message matches the domain name of the sending server.
However, despite the widespread use of SPF, not all email messages pass SPF authentication checks, leading to SPF failures. In this article, we will discuss different types of SPF failure and their causes, as well as steps you can take to minimize the risk of SPF failure for your email domain.
Types of SPF Failure Qualifiers
There are four different types of SPF failure qualifiers that determine the outcome of an SPF check:
- Pass: The message was sent from an IP address authorized by the SPF record of the sending domain.
Here is an example of a pass SPF record:
v=spf1 a mx include:thirdparty.com +all
In this example, the SPF record specifies that email from the domain should come from the domain’s own IP addresses (a and mx) and from the IP addresses of the third-party service specified in the include directive. The +all fail qualifier indicates that messages that do not match the SPF record will be accepted and delivered. This is the most permissive SPF fail qualifier.
- Fail: The message was not sent from an IP address authorized by the SPF record of the sending domain. Here is an example of a fail SPF record:
v=spf1 a mx include:thirdparty.com -all
In this example, the SPF record specifies that email from the domain should come from the domain’s own IP addresses (a and mx) and from the IP addresses of the third-party service specified in the include directive.
The -all fail qualifier indicates that messages that do not match the SPF record will be rejected by the recipient’s email server. This is a harder fail qualifier, which means that the recipient’s email server will reject messages that are not legitimate, without giving them the opportunity to reach the recipient’s inbox.
- SoftFail: The message was sent from an IP address that is not explicitly authorized by the SPF record of the sending domain, but the SPF policy allows for a temporary acceptance of the message. Here is an example of a soft fail SPF record:
“v=spf1 a mx include:thirdparty.com ~all”
In this example, the SPF record specifies that email from the domain should come from the domain’s own IP addresses (a and mx) and from the IP addresses of the third-party service specified in the include directive.
The ~all fail qualifier indicates that messages that do not match the SPF record will be accepted but marked as failed SPF. This is a softer fail qualifier, which means that the recipient’s email server will not reject the message outright, but it will still be able to identify messages that are not legitimate.
- Hardfail – A hard fail result means that none of your email sources passes any tests at all for being legitimate senders; therefore, all mail from such sources should be rejected outright without further consideration by receiving sites like Gmail or Hotmail. Here is an example for Hardfail:
“v=spf1 a mx include:thirdparty.com -all”
In this example, the SPF record specifies that email from the domain should come from the domain’s own IP addresses (a and mx) and from the IP addresses of the third-party service specified in the include directive.
The -all fail qualifier indicates that messages that do not match the SPF record will be rejected by the recipient’s email server. This is a harder fail qualifier, which means that the recipient’s email server will reject messages that are not legitimate, without giving them the opportunity to reach the recipient’s inbox.
- Neutral: The SPF check did not provide a clear result and the recipient email server should use other means to determine the authenticity of the message.
“v=spf1 ?all”
In this example, the SPF record specifies that the recipient’s email server should take no action for messages that do not match the SPF record. The ?all fail qualifier indicates that the recipient’s email server should not pass or fail the SPF check for messages that do not match the SPF record.
This can occur when the SPF record is not properly configured or when the domain does not have an SPF record at all. In this case, the recipient’s email server will not be able to determine if the message is legitimate or not.
- Temperror SPF: Temperror is a status code in SPF (Sender Policy Framework) authentication for email. It means that the SPF check could not be performed because of a temporary error, such as a DNS lookup timeout. It indicates that the email recipient should try again later to verify the sender’s SPF policy.
An example of a temp error in SPF would be if an email server is unable to perform a DNS lookup for the SPF record of the domain in the email’s “From” address due to a temporary issue with the DNS server. The recipient’s email server would then return a “temp error” result, indicating that the SPF check could not be completed and the email should be retried later.
- Premerror SPF: Perm error SPF is a status code in SPF (Sender Policy Framework) authentication for email. It means that the SPF check could not be performed because of a permanent error in SPF, such as a misconfiguration SPF record. It indicates that the SPF check has failed and the email should be marked as potentially fraudulent or rejected.
An example of a permerror in SPF would be if the SPF record for the domain in the email’s “From” address contains a syntax error. This would prevent any email server from correctly evaluating the SPF policy, resulting in a “permerror” result. This would indicate to the recipient’s email server that the SPF check has failed and the email should be treated as potentially fraudulent or rejected.
The most common reason for SPF Fail is that the email provider doesn’t support SPF records so they won’t accept messages from domains using them. Many third party email providers does not support SPF Record published or they have too many lookups. The best thing would be to either not use SPF records or the softfail setting so that emails sent from your domain will still get delivered even though they aren’t passing the SPF check.
There are several common causes of SPF failure, including:
Incorrect SPF Record Configuration: The SPF record for the sending domain may not be configured correctly, either by listing the wrong IP addresses or by including too many IP addresses, causing the SPF record to exceed the maximum length of 255 characters.
Use of Multiple Sending Domains: If a sender uses multiple sending domains, each domain must have its own SPF record that lists the authorized IP addresses for that domain. Failure to set up an SPF record for each domain can result in SPF failure.
Third-Party Services: The use of third-party services, such as email marketing platforms or email relay services, can cause SPF failure if the IP addresses of these services are not listed in the SPF record of the sending domain.
Dynamic IP Addresses: If a sender uses a dynamic IP address, the IP address may change over time, causing SPF failure if the new IP address is not listed in the SPF record of the sending domain.
Misconfigured Email Servers: Misconfigured email servers can cause SPF failure by sending messages from unauthorized IP addresses, or by using the wrong domain name in the “From” field of email messages.
SPF Permanent error: SPF Permanent error or in short SPF PermError is indication that there is some misconfiguration in SPF Records. If there is more than 10 DNS lookups in any SPF Record that would create SPF PermError.
Effects of SPF Failure occurs. SPF failure can have several consequences for both the sender and the recipient of an email message, including:
- Reduced Email Deliverability: SPF failure can reduce the deliverability of emails, as recipient email servers may mark messages as spam or reject them outright.
- Decreased Email Reputation: Reputation-based email filters use SPF failure as a negative indicator of the sender’s reputation, reducing the likelihood of messages being delivered to the recipient’s inbox.
- Increased Risk of Spam and Phishing Attacks: SPF failure can increase the risk of spam and phishing attacks, as malicious actors can use fake email addresses to impersonate the sender and trick recipients into disclosing sensitive information. Dynamic IP Addresses: If a sender uses a dynamic IP address, the IP address may change over time, causing SPF failure if the new IP address is not listed in the SPF record of the sending domain.
- Misconfigured Email Servers: Misconfigured email servers can cause SPF failure by sending messages from unauthorized IP addresses, or by using the wrong domain name in the “From” field of email messages.
How to Fix SPF Fail:
Sometimes SPF can fail, leading to emails being marked as spam or rejected altogether. Here’s how you can fix SPF failures and improve email delivery.
Check your SPF record
The first step in fixing SPF failure is to check your SPF record. SPF records are stored in your domain’s DNS settings and specify which mail servers are authorized to send emails from your domain. Make sure the SPF record is correct and up-to-date. You can use online tools such as MX Toolbox to check your SPF record.
Limit the number of mechanisms in your SPF record
The SPF record has a maximum lookup limit, which means that you cannot have too many mechanisms in your record. The more mechanisms you have, the more likely it is that you will exceed the limit. To minimize the chances of reaching the limit, limit the number of mechanisms in your SPF record.
Use an SPF wizard
An SPF wizard can help you generate a valid SPF record for your domain. These tools simplify the process of creating an SPF record by automatically generating one based on your domain’s mail servers.
Include all mail servers
Make sure that all mail servers sending emails from your domain are included in your SPF record. This helps ensure that all emails sent from your domain are properly authenticated.
Reduce the size of your TXT record
If your SPF record is still too large, consider breaking it down into multiple TXT records. This will reduce the size of each record and help ensure that your SPF record stays within the lookup limit.
Monitor for failures
Regularly monitor your logs for SPF failures and address them promptly. You can use email delivery monitoring tools to track delivery rates and identify any SPF failures. Fixing SPF failures is crucial for ensuring proper email delivery. By following these steps, you can improve the deliverability of your emails and prevent them from being marked as spam or rejected
With SimpleDMARC:
DMARC (Domain-based Message Authentication, Reporting & Conformance) is a protocol that builds on SPF and DKIM to provide a comprehensive email authentication solution.
By enrolling in SimpleDMARC, you can gain greater control over the authentication of emails sent from your domain which will help you to identify the risk of SPF failures. Monitor SPF Results: Regularly monitor the results of SPF checks to identify any issues and resolve them promptly.
In conclusion, enhancing the security of the email system. However, SPF can sometimes fail, which can lead to legitimate emails being marked as spam or blocked. To prevent SPF failures, it is important to ensure that the SPF record is correctly configured, to work with third-party services, and to implement DMARC. By taking these steps, you can reduce the risk of SPF failures and ensure that your email system remains secure and reliable.