How To Manage Multiple SPF Records For
Your Domain Without Complicating Email Authentication

Handling several SPF (Sender Policy Framework) records for your domain can be complex, particularly if you rely on various third-party services to send emails for you. SPF serves as an essential protocol for email authentication, safeguarding against unauthorized individuals sending messages on behalf of your domain. However, managing multiple SPF records necessitates careful attention to avoid conflicts or failures in email authentication. This article aims to provide you with best practices for effectively managing multiple SPF records while ensuring that your email authentication remains clear and efficient.


What is SPF and Why is it Important?


SPF is an email authentication mechanism that allows domain owners to designate authorized mail servers for sending messages on their behalf. By adding an SPF record to DNS settings, recipients can confirm the legitimacy of emails purporting to be from your domain. This system is crucial for preventing email spoofing, where attackers mimic legitimate domains to distribute fraudulent content. However, managing SPF records can be complex, especially with multiple email services, and improper handling may result in delivery problems.



Challenges with Multiple SPF Records


A key challenge with SPF is the restriction of a single SPF record per domain. Having multiple records can result in SPF failures, adversely impacting email deliverability. Below are typical problems encountered when handling multiple SPF records:


  • SPF Lookup Limit: SPF records are restricted to a maximum of 10 DNS lookups. Exceeding this limit may cause emails to fail SPF validation, leading to deliverability problems.

  • SPF Record Conflicts: Creating multiple SPF records for a single domain by error can result in conflicts between them, which may cause issues with authentication.

  • Lack of Alignment with Third-Party Services: External vendors offering services like email marketing, CRM systems, or cloud email providers (e.g., Mailchimp, SendGrid, Salesforce) often require separate SPF records, complicating DNS setup. Incorrect alignment of these records may lead to emails being marked as suspicious or rejected.

Best Practices for Managing Multiple SPF Records


To successfully manage multiple SPF records for your domain without complicating email authentication, follow these best practices:


Consolidate SPF Records Into a Single Record

The most effective way to manage multiple SPF records is to combine them into a single SPF record. SPF only supports one record per domain, so you should gather all authorized senders and services into one comprehensive SPF entry.

Here’s an example of a consolidated SPF record:

v=spf1 include:_spf.google.com include:mailchimp.com include:sendgrid.net ~all

This example includes:


  • Google Workspace (Gmail): _spf.google.com

  • Mailchimp: mailchimp.com

  • SendGrid: sendgrid.net

By using the include mechanism, you can add third-party services like Mailchimp and SendGrid without exceeding the 10 DNS lookup limit.


Use SPF Include Mechanisms to Add Third-Party Services

Utilize the include mechanism to reference the SPF records of other domains, rather than adding numerous IP addresses or subnets for third-party services. This ensures proper authorization of mail servers.

For example, if you are using SendGrid and Mailchimp, you can include their SPF records in your domain’s SPF record as follows:

v=spf1 include:_spf.google.com include:sendgrid.net include:mailchimp.com ~all

By utilizing third-party services, you can assign the responsibility of SPF checks instead of listing all potential IP addresses they may utilize.


Monitor and Optimize SPF Lookups

SPF records are limited to a maximum of 10 DNS lookups, encompassing all included mechanisms. To prevent authentication failures, it is crucial to keep your SPF record within this limit.

To optimize your SPF record:


  • Avoid unnecessary includes: Only include services that are actively sending email on your behalf.

  • Flatten your SPF record: Flattening involves substituting include mechanisms with the actual IP addresses or ranges of a third-party service. While this minimizes DNS lookups, it may complicate record maintenance.


Use a Subdomain for Specific Services

For domains utilizing various email services (such as marketing, transactional, and internal communications), it is advisable to implement subdomains for each service. This approach allows for distinct SPF records, preventing potential conflicts.

For example:


  • Main domain (e.g., yourdomain.com): Used for regular corporate emails with Google Workspace.

  • Subdomain (e.g., marketing.yourdomain.com): Used for marketing emails with Mailchimp or SendGrid.

For the subdomain marketing.yourdomain.com, you can create a separate SPF record, like this:

v=spf1 include:sendgrid.net ~all

This approach allows you to isolate the SPF records for different email use cases, preventing conflicts and simplifying management. Visit www.autospf.com for more details.