SPF Failures: Common Causes and Solutions

[nusaibatara]

Have you ever seen an email that failed SPF authentication?
If yes, I will tell you the exact reason why SPF validation failed. Sender Policy Framework (SPF) is one of the email validation protocols that enterprises have used in their email systems for many years to reduce spam and authorize sending sources. However, due to unfavorable circumstances, if your SPF fails, it may cause potential email sending problems.
1. What is SPF?
SPF is an email validation protocol that verifies that the IP address of an phone number list email sender is authorized to send email on behalf of the domain specified in the "From:" field of the message. When sending an email, the receiving mail server queries the DNS for the SPF record associated with the domain name to check if the sending IP address is listed in the record. If the IP address is not authorized, the email may fail SPF validation.
2. What are the reasons for SPF failure?
Understanding the correct settings for your SPF record is essential to ensure your emails pass authentication checks. This is essential for successful email marketing or sending to win customers. SPF can fail for the following reasons: 1. **When your email fails SPF, the next step should be to find out the reason behind it so that you can fix the problem. **This can be done by regularly monitoring DMARC reports. PowerDMARC gets reports of SPF authentication failures through our SecurityGateway. 2. **When you have an SPF report, the receiving MTA may return any of the following SPF failure results for messages that failed SPF. **Let's take a closer look at them: - **The following are the SPF failure qualifiers, each of which is added as a prefix before the SPF failure mechanism: "+" "Pass" "-" "Fail" "~" "Soft Fail" "?" "Neutral"** - "+" (Pass): If your email does not pass SPF, you can choose how strictly you want the recipient to handle it. You can specify a qualifier to "Pass" the message through (send), "Fail" it, or take a "Neutral" stance (do nothing). - "-" (Fail): In the first case - if the server receiving the email does a DNS query and cannot find the domain name in DNS, a "None" result will be returned. None will also be returned if no SPF record is found in the sender's DNS, which means that the sender has not configured SPF validation for the domain. In this case, SPF validation of the email will fail. - "~" (Soft Fail): Use our SecurityGateway tool to avoid this situation. When configuring SPF for your domain, if you include the "All" mechanism in your SPF record, this means that no matter what the SPF validation check for your outbound mail concludes, the receiving MTA will return a neutral result. This is because when your SPF is in neutral mode, you are not specifying the IP addresses that are authorized to send mail on your behalf, but rather allowing unauthorized IP addresses to send mail. - "?" (neutral): Similar to SPF neutral, SPF softfail is identified by the ~all mechanism, which means that the receiving MTA will accept the email and deliver it to the recipient's inbox, but if the IP address is not listed in the SPF record in DNS, it will be marked as spam, which may be a reason why your email failed SPF validation. - "*" (pass): Below is an example of an SPF softfail. - "hardfail": SPF hardfail, also known as SPF fail, means that the receiving MTA will discard email from any source that is not listed in your SPF record. We recommend that you configure SPF hardfail in your SPF record if you want to gain protection against domain impersonation and email spoofing. Below is an example of an SPF Hardfail. 3. **A very common and usually harmless reason for SPF validation failure is SPF Temperror. ** It is caused by a DNS error (such as a DNS timeout) that occurs when the receiving MTA performs the SPF validation check. So as the name implies, it is usually a temporary error that returns a 4xx status code and may cause SPF to fail temporarily, but you will get an SPF pass result when you try again later. 4. **Another common result faced with domain errors is SPF Permerror. ** This refers to a permanent error with SPF. This happens when your SPF record is invalidated by the receiving MTA. There are many reasons why SPF can be broken and invalidated by the MTA when performing DNS queries: - When the MTA performs, it queries the DNS or does a DNS lookup to check the authenticity of the email source. Ideally, SPF allows up to 10 DNS queries to be made, exceeding this number will cause SPF to error out and return a Permerror result. This is a very common problem that causes SPF to fail.
3. How to solve the SPF failure problem?
To resolve SPF failures, you can follow these SPF best practices: 1. **If your SPF is failing because your DNS queries exceed the limits set by the RFC, try to stay within the limits to prevent SPF failures. ** PowerDMARC helps customers optimize SPF records through macros to stay below these hard limits. The macros in the SPF DNS records can help you stay within the DNS invalidation and lookup limits. 2. **Manual execution of SPF records often results in syntax errors that cause SPF failures. ** To ensure that you use the correct SPF syntax, use automated tools to generate records. These free online tools can generate error-free DNS records instantly. 3. **Always use the resource type "TXT" when configuring SPF in DNS. ** If the wrong resource type is configured, such as "CNAME" or even "SPF", it will result in configuration errors and SPF failures. 4. **Make sure you have correctly authorized all sending sources, including third-party vendors, in your SPF record. ** Your vendors often change or add to the sending IP list. You must ensure that you are aware of these changes and implement them in your own SPF records. Missing an authoritative sending source often leads to unnecessary SPF failures. 5. **Having multiple SPF records for the same domain name can lead to ineffective SPF implementation and result in SPF failures.** In this case, it is best to use the "include" mechanism to merge the records into a single record.