Why Having Multiple SPF Records Can

Cause Issues And How To Fix Them

The Sender Policy Framework (SPF) serves as a crucial email authentication technique employed to identify and thwart email spoofing attempts. SPF operates by enabling domain administrators to outline the authorized mail servers that can dispatch emails on behalf of their domain. This is achieved through the dissemination of SPF records within the Domain Name System (DNS). Nevertheless, the presence of numerous SPF records for a singular domain can lead to substantial complications. 

Understanding SPF Records

SPF records serve as DNS TXT entries that specify the authorized IP addresses or hosts permitted to dispatch emails on behalf of a given domain. Upon receipt of an email, the recipient's mail server scrutinizes the sender's domain SPF record to authenticate the sender's credibility.

Example of an SPF Record

An example of an SPF record might look like this:

v=spf1 ip4:192.0.2.0/24 include:_spf.google.com -all

This record specifies that emails can be sent from the IP range 192.0.2.0/24 and any server included in Google's SPF record (_spf.google.com).

The Problem with Multiple SPF Records

DNS Standard Limitations: 

According to the DNS standard, a domain is limited to having a single SPF record. If multiple SPF records are found, DNS resolvers may encounter issues in processing them accurately, resulting in unforeseeable outcomes. As a consequence, the recipient's email server could potentially disregard one or both of the records, resulting in legitimate emails being incorrectly classified as spam or rejected.

Email Deliverability Issues: 

Having numerous SPF records can lead to confusion for mail servers that receive emails. The presence of multiple SPF records may cause a mail server to encounter difficulties in accurately verifying the sender's IP address. This can result in:

• Email Rejection: Legitimate emails may be rejected because the receiving server cannot validate them against the SPF policy.


• Spam Classification: Emails that should be authenticated and delivered may end up in the spam folder.

Security Vulnerabilities

The presence of multiple SPF records may inadvertently compromise the email security stance of your domain. When distinct records define varying sets of authorized sending IP addresses, it introduces ambiguity that malicious actors can exploit to impersonate emails.

How to Fix Multiple SPF Records

Consolidating SPF Records

The most effective way to resolve the issue of multiple SPF records is to consolidate them into a single SPF record. This involves combining all the authorized sending sources into one unified record.

Steps to Consolidate SPF Records

• Identify All SPF Records: Utilize DNS query tools to pinpoint all current SPF records associated with your domain.


• Merge the Records: Consolidate the SPF records identified into a unified entry, adhering to the 255-character limit for SPF records and the 512-character limit for DNS TXT records. Utilize the include mechanism to incorporate additional SPF records as needed while maintaining compliance with these constraints.

Example:

If you have two SPF records:

v=spf1 ip4:192.0.2.0/24 -all

v=spf1 include:_spf.google.com -all

Combine them into one:

 v=spf1 ip4:192.0.2.0/24 include:_spf.google.com -all

• Publish the New SPF Record: Please ensure that your DNS settings are updated to implement the unified SPF record, which will streamline multiple records into a single, all-encompassing entry.

• Verify the SPF Record: Once you have made the necessary changes to your DNS settings, verify the accuracy and functionality of the new record by utilizing SPF validation tools.

Best Practices for Managing SPF Records

• Keep It Simple: Steer clear of convoluted SPF records. Maintain a concise and relevant list of approved senders.


• Regularly Review and Update: Regularly reassess your SPF record to confirm its accuracy in representing all valid sending sources, and eliminate any that are no longer active.


• Use Subdomains: When managing various email sender groups for distinct purposes, it is advisable to utilize subdomains with dedicated SPF records to efficiently segregate and oversee them.


• Monitor DNS Changes: Monitor DNS modifications and SPF record revisions diligently to avoid the inadvertent generation of duplicate entries.

Having numerous SPF records can lead to notable challenges, ranging from difficulties in email delivery to potential security risks. The key to resolving this is simple: merge all approved sending origins into a unified SPF record. By adhering to recommended guidelines and consistently monitoring your SPF setup, you can uphold a robust email authentication system, guaranteeing the consistent and secure transmission of your emails. See more information about multiple SPF records.