--- title: "The Structure Of SPF Syntax With Tags | DuoCircle" description: "Join the thousands of organizations that use DuoCircle Find out how affordable it is for your organization today and be pleasantly surprised.Interested in" image: "https://www.duocircle.com/images/og-default.png" canonical: "https://www.duocircle.com/content/spf-validator/spf-syntax/" --- Content # The Structure Of SPF Syntax With Tags SPF (Sender Policy Framework) record syntax is built from mechanisms, or tags, that authenticate email senders for a domain. Common tags include a and mx, which validate the sender's IP address; ip4 and ip6, which list permitted addresses; exists, which checks for an A record; and \~all, which flags non-matching mail as suspicious. [ Talk to an Expert → ](/contact/) [ See what we make ](/products/) ## The Structure Of SPF Syntax With Tags The sender policy framework, better known as SPF, is an authentication protocol used to corroborate the authenticity of emails sent or received from a domain. _SPF helps the user shield their domain from forgery or spoofing, thereby providing a secure platform for both the sender and the receiver_. It may initially seem confusing, but SPF syntax becomes straightforward to understand when broken down into individual mechanisms. An **SPF record syntax** consists of various parts. These parts or elements are often termed as mechanisms or tags that form an SPF syntax’s basic structure. They can be analyzed separately and described one by one. [Fix Your SPF Errors Now](/email/spf-record-check) ![spf validator](https://media.mailhop.org/duocircle/images/2021/06/spf-syntax.png) ### SPF Syntax Structure Any typical [SPF record example](/content/spf-validator/spf-record-example) includes tags such as the ones listed below: - **a**: This tag helps one validate the IP address that the sender has used to send an email from their domain. _If it matches the sender’s IP address completely, one can rest assured that it is authentic_. - **mx**: Like the previous mechanism, this too authenticates the IP address of the client who has sent the mail. _If it locates the IP address of the sender within the records, it is safe_. - **ip6 and ip4**: These mechanisms specify the IPv6 and the IPv4 IP addresses, respectively, that can send emails for the domain. - **ptr**: This mechanism is not recommended as per the [RFC 7208 guidelines](https://datatracker.ietf.org/doc/html/rfc7208). Its function is to make sure that a minimum of one **PTR hostname** found in the A record finds an exact match with that of the IP of the sender/ client. - **exists**: This tag runs an ‘A’ record search on the mentioned domain. Its function is to verify the existence of an ‘A’ record. - **\~all**: This mechanism is typically found at the end of the **SPF record**. [SPF \~all](/content/spf-validator/spf-all) has been designed to provide the user or the email receiver with proper advice regarding what steps they can take if there is no such exact match with the SPF record syntax. _The term “\~all” suggests that the email should be treated as suspicious_. Hence, it facilitates the acceptance of the message but flags it to treat it with caution. The **SPF tags** mentioned above constitute SPF records and can be automatically created using [SPF generator](/content/spf-validator/spf-generator) tools. They are of utmost importance to the receiver of the emails since they can verify whether or not the emails are from safe sources. _SPF is one of the oldest and one of the most reliable authentication tools_ (An SPF record can also be tested using an [SPF Validator](/content/spf-validator), which automatically tests it for anomalies). This protection can be further strengthened by adding two further layers, namely the DKIM and the DMARC tools, which were later created following in the footsteps of SPF. ##### Join the thousands of organizations that use DuoCircle --- Find out how affordable it is for your organization today and be pleasantly surprised. [Auto SPF - Sign Up FREE](/email/spf-record-check)Interested in our Partner Program for MSPs and VARs? Visit Our [MSP Partner Program](/msp-partner-program). ## Ready to talk? Same-day response from someone technical. We tell you yes or no quickly. If yes, we get to work. [Talk to an Expert→](/contact/)[See what we make](/products/) ```json {"@context":"https://schema.org","@type":"Organization","name":"DuoCircle LLC","url":"https://www.duocircle.com","logo":{"@type":"ImageObject","url":"https://www.duocircle.com/images/duocircle-logo.png"},"description":"DuoCircle is a portfolio of specialized email products covering protection, authentication, delivery, and routing. We deliver about 90% of category-leader capability at roughly half the price, backed by experts who own the outcome. 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