--- title: "What is Gmail's ‘Best Guess’ SPF Status? | AutoSPF" description: "Gmail sometimes guesses the SPF status of senders lacking an SPF record published in their domain’s DNS." image: "https://autospf.com/og/blog/what-is-gmails-best-guess-spf-status.png" canonical: "https://autospf.com/blog/what-is-gmails-best-guess-spf-status/" --- Quick Answer Gmail sometimes guesses the SPF status of senders lacking an SPF record published in their domain’s DNS. This so-called ‘best guess’ can harm genuine communications or let a spam email pass through; thus, it’s better to shield your domain with SPF so that Gmail doesn’t have to assume authenticity. Let’s give it a closer look. 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This so-called ‘best guess’ can harm genuine communications or let a [spam email](https://www.bloomberg.com/news/newsletters/2023-08-18/qr-code-phishing-spam-email-is-the-next-cybersecurity-threat) pass through; thus, it’s better to [shield your domain with SPF](/blog/how-to-create-an-spf-txt-record/) so that Gmail doesn’t have to assume authenticity. Let’s give it a closer look. ## When does Gmail return SPF “Best Guess” Status? Gmail might generate an SPF “Best Guess” status when the sender’s domain lacks a distinct SPF record in its DNS configuration. In these situations, Gmail attempts to infer the [SPF policy](/generative-ai-and-phishing-threats/spf-record-breakdown/) using historical email data and sender patterns. _While the “Best Guess” status is not as dependable as a clearly defined SPF record, it enables Gmail to offer a degree of email authentication._ Gmail shares no accurate answer on what factors the ‘best guess’ works on, but experts assume it could be [reverse DNS](https://www.cloudflare.com/learning/dns/glossary/reverse-dns/) between the sending IP address and sending domain, email history, and the sender’s behavior. If Gmail has guessed your SPF status, this will be its response- ``` Received-SPF: pass (google.com: best guess record for domain of companyname@domain.com designates 12.43.77.991 as permitted sender) ``` ## What About Other Mailbox Providers? By far, only Gmail synthesizes SPF records or authentication statuses based on the senders’ behavior and history. The impact on your [domain’s email deliverability](https://www.nutshell.com/blog/email-deliverability-guide) is more pronounced when dealing with ISPs like Yahoo, Hotmail, Microsoft Outlook, and others outside the Gmail ecosystem. However, now [Yahoo (along with Google) has mandated DMARC deployment for bulk senders](/blog/ushering-a-new-era-of-security-google-and-yahoos-take-on-email-authentication/); and implementation of DMARC depends on SPF and DKIM. So, indirectly, both _Gmail and Yahoo need you to have SPF, DKIM, and DMARC in place if you want to see your emails in the inboxes of their users._ ![phishing](https://media.mailhop.org/autospf/images/2024/02/kitterman-spf.jpg) ## How Do You Avoid the ‘Best Guess’ For Your Emails? To prevent Gmail from assuming your SPF policy, it’s better you start defining a policy in a clear and concise SPF record and publish it on your domain’s DNS. Here’s what you need to check and do- ### Look for an Existing SPF Record There can’t be more than one SPF record corresponding to a domain. So, begin by verifying no record already exists. Having multiple SPF records nullifies all of them, and your domain becomes [vulnerable to phishing, spoofing, scamming](https://www.businesswire.com/news/home/20230808897517/en/U.S.-Banks-Vulnerable-to-Mass-Social-Engineering-and-Phishing-Attacks---New-Cybersecurity-Report-from-Hush-Ranks-100-Largest), etc. In case you find multiple SPF records, [merge them into one](/blog/merge-spf-records-to-fix-multiple-spf-records-error/). ### Generate a Fresh SPF Record Use an [online SPF record-generating tool](https://mxtoolbox.com/SPFRecordGenerator.aspx) to develop an [SPF record](/explaining-sender-policy-framework-spf-macros/how-to-create-spf-record/), including all the IP addresses and mail servers that you trust and allow to be used for sending messages. Use the right set of syntaxes (mechanisms, modifiers, and qualifiers) to specify instructions for recipients’ email servers. ### Use the Right ‘Fail’ Mechanism There are two types of SPF fail mechanisms: [SoftFail and HardFail](/fix-spf-permerror-and-temperror-a-diy-guide/spf-neutral/). You can set your record to either of them. SoftFail (indicated by \~all) in SPF is like a gentle reminder rather than a strict rejection. It’s like saying, “Hey, this email doesn’t perfectly match the sender’s rules, but we’ll let it through with a raised eyebrow.” It’s a bit more forgiving, recognizing that some legitimate emails might not align perfectly with the specified policies due to things like forwarding or [mailing lists](https://en.wikipedia.org/wiki/Mailing%5Flist). While SoftFail doesn’t slam the door shut on an email, it does raise a caution flag and place it in the spam folder, prompting the receiving server to take a closer look or apply additional checks. On the other hand, SPF HardFail is like a firm handshake with rules. If an email gets a HardFail, it means the SPF check is saying, “This email doesn’t follow the rules, so let’s not take any chances.” It’s a strict approach, usually marked by a [“-all” qualifier in the SPF record](/spf-record-tester/spf-record-all/). In this case, the email might face rejection, be treated as spam, or undergo more rigorous scrutiny. ### Publish the SPF Record After producing an SPF record and mentioning all the sending sources along with instructions for recipients’ mailboxes, add it as a [DNS TXT record](https://dnsmadeeasy.com/post/what-is-a-txt-record) in your domain’s DNS settings. You can do this by navigating to your domain registrar’s control panel or DNS management interface. ![spf record](https://media.mailhop.org/autospf/images/2024/02/multiple-spf-records-2332.jpg) ### How Do You Verify it? Lastly, make sure your record is non-erroneous and is working properly. Do this by running it through a credible online [SPF lookup tool](/spf-record-tester/kitterman-spf/) (also called as [SPF record checker](/spf-record-checker/spf-record-example/)). There are chances that your SPF record will come across the ‘[too many DNS lookups error](/spf-too-many-dns-lookups/spf-lookup/)’ that arises if you exceed the maximum lookup limit of 10\. In such cases, visit us for [automatic SPF record flattening](/) that compresses your record and resolves the issue in no time so that your domain strongly fortifies [cyber menaces](https://www.forbes.com/sites/investor/2023/12/14/cybersecurity-stocks-to-consider-amid-the-growing-menace-of-cyberattacks/?sh=11a80ecf75b7). ## Topics [ email security ](/tags/email-security/)[ SPF ](/tags/spf/)[ SPF record ](/tags/spf-record/) ![Brad Slavin](https://media.mailhop.org/autospf/images/authors/brad-slavin.jpg) [ Brad Slavin ](/authors/brad-slavin/) General Manager Founder and General Manager of DuoCircle. Product strategy and commercial lead for AutoSPF's 2,000+ customer base. [LinkedIn Profile →](https://www.linkedin.com/in/bradslavin) ## Ready to get started? Try AutoSPF free — no credit card required. [ Book a Demo ](/book-a-demo/) ## Related Articles [ Intermediate 3m 3 points to consider before setting your SPF record to -all (HardFail) May 22, 2025 ](/blog/3-points-to-consider-before-setting-your-spf-record-hardfail/)[ Intermediate 3m 5 key contributors to the development of the Sender Policy Framework Nov 12, 2024 ](/blog/5-key-contributors-to-sender-policy-framework-development/)[ Intermediate 5m Are Your SPF and DKIM Identifiers Aligned? Jul 18, 2024 ](/blog/are-your-spf-and-dkim-identifiers-aligned/)[ Intermediate 6m Automated Solutions for Preventing Email Spoofing May 7, 2026 ](/blog/automated-solutions-for-preventing-email-spoofing/) ```json {"@context":"https://schema.org","@type":"Organization","@id":"https://www.wikidata.org/wiki/Q138897474","name":"AutoSPF","url":"https://autospf.com","logo":{"@type":"ImageObject","url":"https://autospf.com/images/autospf-logo.png"},"description":"Automatic SPF flattening and email authentication management. 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Resolve SPF lookup limits, flatten SPF records, and maintain email deliverability across all your domains.","parentOrganization":{"@type":"Organization","@id":"https://www.wikidata.org/wiki/Q138883901","name":"DuoCircle LLC","url":"https://www.duocircle.com","sameAs":["https://www.wikidata.org/wiki/Q138883901","https://www.crunchbase.com/organization/duocircle-llc","https://www.linkedin.com/company/duocircle","https://github.com/duocircle"],"subOrganization":[{"@type":"Organization","@id":"https://www.wikidata.org/wiki/Q138898167","name":"DMARC Report","url":"https://dmarcreport.com"},{"@type":"Organization","@id":"https://www.wikidata.org/wiki/Q138897474","name":"AutoSPF","url":"https://autospf.com"},{"@type":"Organization","@id":"https://www.wikidata.org/wiki/Q138897912","name":"Phish Protection","url":"https://www.phishprotection.com"}]}}} ``` ```json {"@context":"https://schema.org","@type":"BlogPosting","headline":"What is Gmail's ‘Best Guess’ SPF Status?","description":"Gmail sometimes guesses the SPF status of senders lacking an SPF record published in their domain’s DNS.","url":"https://autospf.com/blog/what-is-gmails-best-guess-spf-status/","datePublished":"2024-02-09T17:17:47.000Z","dateModified":"2026-04-18T02:36:41.000Z","dateCreated":"2024-02-09T17:17:47.000Z","author":{"@type":"Person","@id":"https://autospf.com/authors/brad-slavin/#person","name":"Brad Slavin","url":"https://autospf.com/authors/brad-slavin/","jobTitle":"General Manager","description":"Brad Slavin is the founder and General Manager of DuoCircle, the company behind AutoSPF, DMARC Report, Phish Protection, and Mailhop. 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