What Is SPF Email Record? Function, Syntax, and Errors

Did you know that every 39 seconds, a cyberattack takes place somewhere in the world, often starting with a simple forged email? The consequences can be devastating. Businesses risk losing client trust and suffering a brand reputation that may never recover. One of the most common tricks behind these attacks is domain spoofing, where criminals impersonate trusted domains to deceive recipients. 

The good news is that the SPF email record, also known as Sender Policy Framework, can step in as your strongest line of defense. In this guide, you will learn what the SPF email record is, why it matters, and how it can protect your domain from spoofing.

What Is SPF Email Record?

The SPF policy, defined in the DNS record, lists the mail servers authorized to send messages on behalf of your domain. More specifically, the Sender Policy Framework (SPF) is an email authentication protocol that works like a guest list for your domain. Imagine hosting an exclusive event where only invited guests can enter. In the same way, SPF lets you create a list of servers that are officially allowed to send emails on your domain’s behalf.

The primary purpose of SPF is to prevent unauthorized senders from impersonating you, thereby blocking email spoofing attacks. As a bonus, implementing SPF can also improve your email deliverability and strengthen your sender reputation, making it more likely that legitimate emails reach inboxes instead of spam folders.

From a technical standpoint, SPF is a type of TXT record that you publish in your domain’s DNS (Domain Name System). This record informs receiving mail servers about trusted sources, ensuring that your domain identity cannot be easily faked.

How Does an SPF Email Check Actually Work?

SPF lets a domain owner publish a DNS TXT record that lists the mail servers by IP or hostname that may send on that domain’s behalf. Think of it as your approved sender list. 

Here is how SPF works step-by-step:

1. Publish an SPF record in your DNS

The foundation of SPF begins with the Domain Name System (DNS). DNS is the infrastructure that maps human-readable domain names, such as example.com, to the IP addresses that computers and servers use to communicate. It ensures that when an email is sent, the receiving server can locate and verify the domain it claims to come from.

For SPF to function, the domain owner must publish an SPF record within their domain’s DNS. This record takes the form of a TXT record that specifies which mail servers, identified by IP addresses or hostnames, are authorized to send emails on behalf of the domain.

Publishing the SPF record is a mandatory first step. Without it, there is no reference point for receiving mail servers, meaning SPF checks cannot be performed at all.

2. Send an email from your domain

The SPF verification process begins the moment an email is sent. Each outgoing message carries information about the sender’s domain, most importantly in the Return-Path address (also called the envelope sender or MAIL FROM address). This address not only directs where bounced or undeliverable emails should be returned, but it also identifies the domain that will be checked against the SPF record.

This step is the trigger event for the entire SPF verification workflow. Without the act of sending and declaring the domain in the Return-Path, there is nothing for the receiving server to validate. From this point forward, the recipient’s mail server begins the process of checking whether the sending server is authorized according to the published SPF record.

3. Identify the sender’s domain from the email header

Once the email reaches the recipient’s mail server, the next step is to determine which domain should be checked. To do this, the server looks at the Return-Path address, also known as the envelope sender or MAIL FROM address. This field is important because it specifies where any bounced or undeliverable messages should be returned.

It’s important to note that SPF checks are based on the technical Return-Path address, not the visible “From” address that appears in a user’s inbox. Attackers often try to exploit this difference by forging the display “From” field to mislead recipients.

4. Look up the domain’s SPF email record

Once the sender’s domain is identified, the receiving server needs to verify which servers are authorized to send email for that domain. To do this, it looks up the domain’s SPF record in DNS. DNS, or the Domain Name System, works like the internet’s public address book, translating domain names into information that servers can read.

The server specifically searches for a TXT record that begins with v=spf1, which contains the list of authorized sending servers. This record tells the server whether the email came from an approved source and is a crucial step in the SPF verification process.

5. Compare the sender’s IP address to the record

The SPF record contains a policy that defines which servers are allowed to send emails for the domain. The recipient’s email server compares the IP address of the server that sent the email against the list of authorized servers specified in the SPF record. The return path email address is cross-checked at the receiver’s end to verify whether or not the sending IP address is listed in the SPF records.

6. Determine the SPF authentication result

After checking the SPF record, the receiving server determines the authentication result.

Possible results include:

• Pass: The sending IP address is listed as an authorized sender.
• Fail: The sending IP address is not authorized, and the email should be rejected.
• SoftFail: The sending IP is likely unauthorized, but the email is accepted with caution.
• Neutral: No specific assertion is made about the sending IP address.
• None: No SPF record exists for the domain, so no verification is possible.

7. Take action based on the result

The recipient’s email server takes action based on the SPF check result and the domain’s DMARC policy (if one exists). It could accept the email, mark it as spam, or reject it entirely. If the approval is positive, emails are typically sent to the inbox; otherwise, it may lead to SPF failure.

Set Up SPF with PowerDMARC!

How to Enable and Use Your SPF Email Record

Before you can take advantage of SPF, it’s important to understand what it does and confirm that both your domain and your email service provider support it. SPF on its own authenticates the sending server, but it does not verify the actual identity of the sender or the content of the message. For this reason, SPF works best when combined with additional protocols such as DKIM and DMARC, and even BIMI, to create a stronger and more complete email authentication framework.

Once you’re ready to implement SPF, the process involves creating and publishing an SPF record in your domain’s DNS. This record clearly defines which servers are authorized to send emails using your domain name, helping receiving mail servers filter out unauthorized or spoofed messages.

To enable SPF for your email, you’ll need to:

Determine the authorized email servers

Identify the IP addresses or hostnames of all email servers that are authorized to send emails on behalf of your domain. This includes your own organization’s email servers, third-party email service providers (like Google Workspace, Microsoft 365, SendGrid, Mailchimp, etc.), and any other services that send email using your domain name. Collect a comprehensive list of all these IP addresses and sending domains.

Define your SPF policy

Determine the policy for SPF. This involves specifying which servers are allowed to send emails for your domain using SPF mechanisms. You also need to decide how strictly receiving servers should enforce the policy using qualifiers (e.g., `-all` for Fail, `~all` for SoftFail).

Construct your SPF format

SPF records are published as a TXT record in your domain’s DNS. The record should be in a specific format, starting with `v=spf1` followed by mechanisms, modifiers, and a final `all` mechanism with a qualifier.

Publish the SPF record

First, generate your SPF record. You can use our free SPF generator tool or manually construct the record based on your authorized senders and policy. Then, access your domain’s DNS management system, which is typically provided by your domain registrar or hosting provider. Locate the DNS settings for your domain and add a new TXT record. Specify the hostname (usually “@” or blank for the root domain itself) and paste the complete SPF record string into the value/data field.

SPF Record Syntax

An SPF record has a specific structure that receiving mail servers use to verify authorized senders.

The main parts of an SPF record include:

• v=spf1: Specifies the SPF version being used.
• Mechanisms: Define which servers are allowed to send email for your domain. Common mechanisms include `a`, `mx`, `ip4`, `ip6`, `include`, `exists`, and `all`.
• Qualifiers: Indicate how strictly the mechanism should be enforced. Examples are `+` (Pass), `-` (Fail), `~` (SoftFail), and `?` (Neutral).
• Modifiers: Provide additional instructions or exceptions to the rules, such as `redirect` or `exp`.

Each of these components is explained in detail in the comprehensive SPF syntax guide, which also includes examples of valid SPF records and how to structure them for different scenarios.

How to Check Your SPF Email Record

Once you’ve set up your SPF record, it may take some time (up to 48 hours, though often much less) for the DNS changes to propagate across the internet. Use our SPF record check tool to validate and test your record. This helps verify the correctness of the syntax and ensures it is being recognized by DNS servers.

It’s important to note that SPF records can be complex, depending on the specific requirements of your email infrastructure. If you’re unsure about the syntax or need more advanced configurations, it’s recommended to consult your system administrator, IT support, or an email authentication expert for assistance in creating the SPF record correctly.

Avoid these Common SPF Email Mistakes

Misconfigurations can make your SPF policy ineffective or block legitimate emails.

Avoid these common pitfalls:

• Using multiple SPF records: Combine all sending services into a single record to prevent validation errors.
• Incorrect syntax: Ensure proper syntax and mechanism usage to avoid record invalidation.
• Not including all authorized senders: List every server and third-party service that sends email for your domain.
• Exceeding the 10 DNS lookup limit: Keep mechanisms under the lookup limit to ensure SPF works correctly.
• Exceeding character limits: Stay within 255 characters per string and overall DNS size limits.
• Using the wrong record type: Always publish SPF as a TXT record, not a deprecated SPF type.
• Failing to update: Update your SPF record whenever you add or remove email services or servers.

Make Your SPF Email Policy More Powerful with PowerDMARC

Implementing an SPF email record is a critical step in protecting your domain from spoofing, phishing, or email spam. By correctly setting up and maintaining your SPF record, you ensure that only authorized servers can send emails on your behalf and safeguard your brand reputation.

Understanding SPF syntax, avoiding common misconfigurations, and combining SPF with DKIM and DMARC strengthen your email authentication strategy and reduce the risk of fraudulent emails reaching your recipients.

For those looking to take their email security further, exploring SPF in more depth and using reliable tools can make a significant difference. PowerDMARC offers easy-to-use solutions to monitor, manage, and optimize your SPF records, helping you keep your domain safe and your emails trusted.

Frequently Asked Questions

What are some SPF email record limitations?

SPF can only verify the sending server, not the sender’s identity or email content. It also has a 10-DNS-lookup limit and strict syntax requirements.

Is SPF the same as DKIM?

No. SPF validates the sending server, while DKIM uses cryptographic signatures to verify that the message content hasn’t been altered.

Why would an email fail in SPF?

An email can fail if it’s sent from an unauthorized server, the SPF record has syntax errors, or the DNS lookup limit is exceeded.

• About
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Maitham Al Lawati

Cybersecurity Expert, CEO at PowerDMARC

Maitham is a tech entrepreneur, cybersecurity expert, CEO and Founder of PowerDMARC with 15+ years of industry experience. Maitham holds a Global MBA from the University of Manchester and various professional certifications including CISSP, CISM, CRISC, and ISC2 CCSP.

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