How to Optimize SPF Record?

Maitham Al Lawati

9 months ago

Key Takeaways

SPF is a crucial email authentication protocol that helps prevent email spoofing by specifying authorized IP addresses for sending emails.
Publishing a correctly formatted SPF record in your domain’s DNS is essential for ensuring proper email delivery and preventing spam classification.
Exceeding the 10 DNS lookup limit when configuring SPF can lead to errors and result in email delivery issues.
Regularly checking and optimizing your SPF record can help avoid common challenges, such as syntax errors and multiple SPF records for the same domain.
Using automated tools can simplify the process of managing and optimizing your SPF record to meet email security standards efficiently.

An optimized SPF record is a key factor that directly impacts your email deliverability and protection against spoofing. A poorly configured or outdated SPF record can lead to failed authentication checks, a poor sender reputation, or even legitimate emails being misclassified as spam.

That’s why fine-tuning and maintaining your SPF record is crucial for any organization sending emails at scale. With PowerSPF, PowerDMARC’s Hosted SPF management service, you can simplify SPF record optimization, ensuring your record always stays valid, efficient, and under the 10 DNS lookup limit without manual intervention.

What is SPF and Why It Matters

Sender Policy Framework (SPF) is an email authentication protocol that helps you authorize senders for your domain. Without an SPF record, your domain gets a free pass, enabling everyone, including threat actors, to send emails on your behalf! While SPF cannot be used by itself to take action against spoofing, when combined with DMARC, it serves as a strong defense against impersonation attacks.

To round up, SPF is crucial because:

It helps domain owners define who is permitted to send emails on their behalf
It works in combination with DMARC and DKIM to prevent spoofing
It helps reduce spam and improve deliverability

Common SPF Issues that Break Deliverability

1. Exceeding the 10 DNS Lookup Limit

SPF allows a maximum of 10 DNS lookups. Going over this limit causes your SPF check to return a PermError, breaking authentication. One of the primary reasons why this may occur is the use of too many “include” mechanisms, which is common when using multiple third-party email vendors.

2. Multiple SPF Records

Having more than one SPF record for the same domain confuses mail servers and invalidates SPF checks. It is always advised to combine all authorized senders into a single DNS record through the process of merging SPF records by using “includes”.

3. Syntax or Configuration Errors

A missing colon, extra space, or misused tag can make your SPF record invalid. Always double-check syntax before publishing and validate your record using our SPF checker tool for instant, and accurate verification.

4. Too Many Void Lookups

When an SPF mechanism points to a domain that doesn’t exist, it results in a void lookup. More than 2 void lookups can trigger SPF permerror and break the authentication flow. It’s important to regularly audit your SPF mechanisms to ensure all domains are valid and active.

SPF Record Optimization Best Practices

The following best practices are expert-recommended advice on maintaining clean, error-free SPF records:

Make an inventory of all your legitimate email sources in decreasing order of importance from left to right in your SPF record
Remove obsolete email sources from your DNS
Use IP4/IP6 mechanisms instead of A and MX
Keep your number of “include” mechanisms as low as possible and avoid nested includes
Use SPF flattening or SPF Macros to optimize SPF records and limit lookups.
Do not publish more than one SPF record for the same domain in your DNS
Make sure your SPF record doesn’t contain any redundant white spaces or syntax errors

SPF Flattening: When and When Not to Use It

SPF flattening converts mechanisms like “include” into a single list of IP addresses, which can significantly reduce the number of DNS lookups in your SPF record.

Pros:

Flattening your SPF record helps simplify the record, so receiving servers can process the authentication faster
It reduces DNS lookup to help you stay under the limit in most cases
It can minimize DNS timeout risks

Cons:

Whenever your ISP makes changes to its IP addresses, you have to manually update your record, too
Simplifying includes into corresponding IPs can make your record really long, exceeding the 255-character limit per string or 512 bytes for the DNS response

Check out our list of Best SPF Flattening Tools.

How Dynamic SPF Flattening Solves the Problem

PowerDMARC’s dynamic flattening solution helps minimize the issues with manual flattening by continuously scanning provider includes and IP addresses, and enabling automatic flattening of all included domains.

Optimize SPF Automatically with PowerSPF

You can certainly optimize your SPF record manually, but why deal with the complexity and risk of errors when you don’t have to? With PowerSPF, our Hosted SPF management solution, you can optimize your SPF record automatically with just a single click. PowerSPF empowers you to:

Leverage SPF Macros to stay within SPF hard limits, including DNS, void, and character length limits.
Easily add or remove sending sources without touching your DNS manually
Update records seamlessly, ensuring your SPF is always accurate and up-to-date
Get a fully optimized SPF record instantly, keeping you under the 10 DNS lookup limit
Mitigate PermError risks before they affect your email deliverability
Eliminate syntax errors and misconfigurations, saving you time and headaches
Automatically resolve SPF limitations, so you never have to worry about them again

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