SPF Record Checker

Analyzing SPF Records for Email Authentication

The Sender Policy Framework (SPF) is a foundational email authentication protocol that helps domain owners prevent unauthorized senders from spoofing their domains. An SPF record is a DNS TXT record that lists the authorized IP addresses and mail servers allowed to send emails on behalf of a specific domain.

When a receiving mail server processes an incoming message, it evaluates the SPF record of the sender's domain to verify if the sending server's IP address is authorized. Properly configuring and maintaining these records is essential for maintaining email deliverability and protecting your domain's reputation. The SPF Record Checker is designed to assist domain administrators, mail configuration personnel, and anyone looking to break down SPF record terms, estimate DNS lookups, and spot syntax or policy risks.

How the SPF Record Checker Works

The SPF Record Checker performs a local syntax check and estimates first-record lookups directly within your browser. It processes the text you provide to break down its terms, estimate the number of DNS lookups it will trigger, and identify potential syntax errors or policy risks.

Because this tool operates entirely locally, it does not query DNS, expand provider records, test a sender IP, or confirm what a receiving mail server will return. Instead, it acts as a review aid by analyzing the provided text string. If your SPF record contains quoted DNS TXT chunks, the tool automatically joins them before performing its analysis.

To use the tool, you must provide an SPF TXT value as an input. This text string represents your SPF record and must begin with v=spf1. The tool supports inputs up to a maximum length of 20,000 characters. If the input is empty, the tool displays the error message Paste an SPF record first.. If the input exceeds the character limit, it flags the error That record is unusually large. Keep it under 20,000 characters.. For unsupported formats, it displays Enter a supported SPF record..

Understanding the Tool Outputs

Once the tool processes your record, it generates a comprehensive SPF analysis and SPF summary containing several key metrics and structured tables:

• Direct DNS terms: A count representing the estimated DNS lookups triggered by the record.
• Mechanisms: The total count of mechanisms found in the record.
• Risks: A count of non-informational risks and policy issues identified during the check.
• Parsed terms: A detailed breakdown of each term found in the record, displayed in a table with the following columns:
  • Term: The specific SPF term analyzed.
  • Kind: The type of term, classified as Mechanism, Modifier, Version, or Unknown.
  • Value or qualifier: The value associated with the term or its qualifier (such as +, -, ~, or ?).
  • Uses DNS: Indicates Yes or No depending on whether the term triggers a DNS lookup.
• Syntax and policy notes: A list of identified issues. If the record is perfectly structured and free of policy risks, the tool displays No syntax or policy risk was found in the pasted record.

The 10-Term DNS Lookup Limit and Its Implications

One of the most critical constraints of SPF evaluation is the strict limit on DNS lookups. To prevent Denial of Service (DoS) attacks on DNS infrastructure, the SPF specification dictates that the maximum allowed DNS lookups during a full evaluation is 10.

The DNS lookup estimate calculated by the tool counts the following terms present in the pasted record:

• include
• a
• mx
• ptr
• exists
• redirect

If the pasted record contains more than 10 DNS-triggering terms, the tool flags the issue: This record already contains ‹detail› DNS-triggering terms, above the SPF limit of 10.

It is important to note that include or redirect targets may add more DNS lookups than the first-record estimate, as they point to external records that may contain their own DNS-triggering terms. If the complete recursive evaluation of an SPF record exceeds the 10-term DNS lookup limit, SPF receivers must treat the evaluation as a permanent error. This can lead to authentication failures and cause legitimate emails to be blocked or marked as spam.

Identifying Syntax Errors and Policy Risks

The SPF Record Checker flags a wide range of syntax errors and policy risks to help you optimize your record:

• Version Issues: The record must begin with v=spf1. Furthermore, v=spf1 must be the first term, and the record cannot contain more than one v=spf1 term. Violations trigger issues such as The record must begin with v=spf1., Term ‹term›: v=spf1 must be the first term., or The record contains more than one v=spf1 term..
• Unrecognized and Malformed Terms: Unknown SPF mechanisms are flagged with Term ‹term›: “‹detail›” is not a recognized SPF mechanism. Missing or malformed mechanism values trigger Term ‹term›: the ‹detail› value is missing or malformed.
• IP Address Validation: Invalid IPv4 or IPv6 addresses and CIDR ranges are flagged with Term ‹term›: enter a valid IPv4 address or CIDR range or Term ‹term›: enter a valid IPv6 address or CIDR range.
• Modifier Restrictions: Duplicate modifiers trigger Term ‹term›: the ‹detail› modifier appears more than once. Additionally, a modifier cannot have a +, -, ~, or ? qualifier; doing so flags Term ‹term›: a modifier cannot have a +, -, ~ or? qualifier..
• The "all" Mechanism and Unreachable Terms: Having more than one all mechanism makes the policy harder to review. Any terms placed after all are unreachable during SPF evaluation. Furthermore, the redirect modifier is ignored if the record also contains all.
• Deprecated and Insecure Mechanisms: The ptr mechanism should not be published because it is slow and unreliable. Using +all is highly discouraged because it authorizes every sender on the internet, which usually defeats the purpose of SPF. Using ?all returns a neutral result, which gives receiving mail servers little policy guidance.
• Missing Terminal Policy: If the record has neither all nor redirect, unmatched senders receive a neutral result, leaving the domain's policy ambiguous.

Privacy and Processing

Your privacy is fully respected when using this tool. Your SPF record stays in your browser; BroBroGo does not upload or save it. Because the page does not query DNS, expand provider records, test a sender IP, or confirm what a receiving mail server will return, no external network requests are made to analyze your record. This ensures that your configuration drafts remain entirely private and secure during your review.

Frequently Asked Questions

How is the SPF DNS lookup estimate calculated?

The estimate counts include, a, mx, ptr, exists and redirect terms in the pasted record. Included and redirected records can add more lookups, so a local check cannot know the final recursive total.

What happens if SPF needs more than 10 DNS lookups?

SPF receivers must treat an evaluation that exceeds the 10-term DNS lookup limit as a permanent error. The limit covers the complete include and redirect chain, not only the first record.

Does a clean result prove that my SPF setup works?

No. This page checks only the text you paste. It does not query DNS, expand provider records, test a sender IP or confirm what a receiving mail server will return.