Fix SPF Permerror: Overcome Too Many DNS Lookups

Listen to this blog post below

 

A little prudence in following the correct practices with your SPF record can create a world of difference in eliminating unwanted SPF Permerrors caused by increased DNS lookups.

SPF, or Sender Policy Framework, is a valuable tool for email authentication that can protect organizations from financial and reputation losses. SPF authentication can prevent malicious actors from phishing and spoofing attempts targeting any reputed organization. However, improper use of SPF records or their incorrect configurations can create more load on them, resulting in email authentication failures.

In other words, such instances increase the number of DNS lookups and result in the SPF Permerror. It can turn the entire authentication process into a disadvantage to the organization rather than a benefit. This article aims to clarify SPF Permerror meaning, the reasons for such errors, and tips to overcome the increased number of DNS lookups leading to SPF Permerror.

What is SPF Permerror?

SPF Permerror or SPF permanent error is an error faced by an email receiving server when it attempts to validate an incoming email by verifying the SPF record of the sender. The Permerror often occurs when the validation faces an unresolved difficulty even after too many DNS lookups.

Image sourced from rejoiner.com

Usually, the maximum DNS lookups allowed is set to 10, and if it exceeds this limit, it results in an SPF Permerror. The root cause for too many DNS lookups is often the improper configuration of the SPF record. When an email results in SPF Permerror, the SPF authentication fails, and the message lands in the junk mail section.

Reasons for SPF Permerror Due to Too Many DNS Lookups

The predominant reasons resulting in issues with SPF validation, leading to too many DNS lookups and SPF Permerror, are the following:

• Complex SPF Records: If an organization attempts to handle many different email sources, its SPF record can become complicated with many mechanisms and ‘include’ statements, resulting in increased DNS lookups.
• Third-Party Validation: Often, organizations deal with several third-party agencies for marketing and customer support services. Such communications will also increase the number of DNS lookups.
• Excessive ‘Include’ Statements: ‘Include’ statements used in an SPF record to include other SPF records can also increase the number of DNS lookups. Sometimes, the included SPF records can also have their ‘include’ statements, making matters worse.
• Extra Domains: Some organizations have multiple domains with a separate SPF record for each domain. In such cases, each SPF record will need validation using individual lookups.

How to Overcome SPF Too Many DNS Lookups?

SPF Permerror resulting from too many DNS lookups can have undesirable consequences. However, one can avoid such a situation and fix SPF errors quickly by following the below-listed steps prudently:

Reduce ‘Include’ Statements:

An ‘include’ statement will redirect the validation process to another domain’s SPF record to include all IP addresses associated with the organization. Make sure no unnecessary ‘include’ statements are used. Wherever possible, ‘include’ statements must be replaced with an appropriate mechanism. This practice will help reduce the number of DNS lookups. 

Replace ‘Include’ Statements with ip4 and ip6 Mechanisms:

If you have many ‘include’ statements in your SPF record, some may be eliminated using the ip4 and ip6 mechanisms. These mechanisms will help you cover multiple IP addresses under a single ‘include’ statement. Thus, you can reduce the total number of ‘include’ statements, reducing the DNS lookup count.

Flatten SPF Records:

SPF record flattening is a method that helps you reduce DNS queries by replacing various mechanisms and modifiers with IP addresses. Every time a mechanism or modifier is replaced this way, the DNS lookup count is reduced by one.

Eliminate Redundant Mechanisms:

An ‘include’ mechanism in a domain’s SPF record may sometimes encompass another domain. In such cases, the latter domain does not need the mechanism again. Such instances must be verified, and unnecessary mechanisms must be removed to eliminate redundant lookups.

Remove ‘ptr’ Mechanisms:

Though the ‘ptr’ mechanism was once used widely, SPF specifications no longer encourage its use due to its drawbacks causing a drastic increase in the number of lookups. Therefore, the ‘ptr’ mechanism must be avoided at all costs.

Stop Validating Unused Domains:

You must check for your active domains periodically to ensure no SPF record mechanism refers to a domain no longer in use. For example, sometimes, you may terminate relations with a third-party vendor. In such a case, including a mechanism in the SPF record for their domain would be useless and only increase the DNS lookup count. Such domain references must be excluded promptly to eliminate SPF Permerror.

SPF Best Practices to Reduce Errors

The following best practices can help maintain a healthy SPF record and email security posture for your organization:

• Updating: Check and update your SPF record routinely to remove any unnecessary entries and include new ones promptly. 
• Testing: Using an efficient SPF testing tool, test the SPF record for correctness after any changes. 
• Creating Awareness: Create awareness among employees by training them concerning SPF best practices and methods to reduce SPF Permerrors. 
• Seeking Professional Assistance: If your organization has a complex email system that makes handling SPF records cumbersome, seek professional assistance from any efficient email security agency. 
• Leveraging DKIM and DMARC: Leverage the power of DKIM (DomainKeys Identified Mail) and DMARC (Domain-based Message Authentication Reporting and Conformance) along with SPF to enhance email security.

Final Words

While SPF email authentication can be invaluable for your business, its incorrect use can render it more harmful than beneficial. SPF Permerror caused by increased DNS lookups can be a stumbling block to any organization with far-reaching implications for its business operations. 

However, one can easily overcome such situations and fix SPF errors by meticulously following the above mentioned methods and best practices. A thorough inspection of your SPF records and periodic verification of your active and inactive domains can provide you with valuable insights to correct any errors. Moreover, using some of the numerous workarounds to make an SPF record lighter can create a world of difference.