What Is An SPF Record Syntax And How Does It Work?

An SPF Record is a TXT record that is part of a domain's DNS record. The TXT record specifies what IP addresses are authorized to send email on behalf of the domain. The SPF Record Syntax is a standard format that is used to specify the IP addresses that are authorized to send email for a domain. 

The Sender Privacy Framework (SPF) record is a vital component of the Domain-based Message Authentication, Reporting and Conformance (DMARC) protocol that specifies a method for deterring sender address forgery. To find out more about spf syntax, visit a website.
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What Is An SPF Record?

SPF record is a kind of DNS record that lists servers that are allowed to send emails from your domain. It does this by recording which servers have permission to send emails from your domain; if you get a message originating from an email server not listed there, it will be rejected as an unauthorized sender.
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SPF records were created to stop malicious users from falsifying emails by sending them using your domain in the From field. This could happen if the user directs a large number of spam e-mail to your server from adventitious means.

How Does SPF Work?

Creating An SPF Record Syntax

You install a special SPF record syntax in your DNS server that specifies IP addresses that are allowed to use your domain for sending emails. This structure means that any message sent from your mail server using an unauthorized IP address would be refused.
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DNS Lookup

When an email recipient tries to send a message, the server will validate that the domain is not disguising itself by looking up domains to see whether the receiving server has an SPF authorization record. The validation has a limit of 10 lookups, so exceeding that can lead to SPF permission error.

If there are no SPF records, authentication fails, and the message is not delivered. If there is an SPF record, the SPF server looks for IP addresses in the TXT record at the hostname specified in the SPF record.

For hosts that need to authenticate themselves, if there are no IP addresses specified, it will fail authentication. Otherwise, for originating hosts, A will perform a query for each unique IP address specified in the order of appearance in the TXT record.

Any IP address that yields a result of NXDOMAIN or NOERROR will be considered authorized for use by the SPF server and will be added to the list of authorized sending hosts for that domain.
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 Authentication Outcome

The mail server either gives the message to its recipient or sends it to the recipient again if it is not in the permissible set of records.

An authentication result can take one of three forms: Pass, Neutral, or Fail.

Mail server passes the information as legitimate and allows it to go through. Neutral indicates that hostname could not be verified in the DNS database; there is no record permitting one to tell if the message is genuine. Fail indicates that something about this message failed; therefore, it doesn't go through.
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SPF Record Syntax

The SPF record syntax includes directives, qualifiers, and mechanisms.

Directives are the very first part of a SPF record syntax. They allow you to interpret the rest of the record. Three directives may show up within an SPF record v spf1, a, and mx. The v directive indicates this record is an SPFv1 record, the a directive states that this is a SPFv2-style authentication failure report, and the mx directive contains a list for mail exchange servers for a domain.
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The qualifiers exim4, enduser, or spf used to designate where to place an IP address belonging to your SPF mail records are connected with DNS zones.
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• all mechanisms will accept any email from senders who have passed your SPF check.
• none mechanism will deny anything from consumers who have passed your SPF examination.
• Emails from senders who failed SPF checks will be accepted as softfails, but will be marked as suspicious.

• It states that you neither accept nor deny an incoming message sent by your domain, so you basically have a non-opinion on whether the message is to be accepted or rejected.
• reject mechanism will reject emails that failed the SPF check.
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Overall, SPF records are an essential security measure for email servers, and they're easy to set up. They're also relatively simple to understand and maintain, so you don't need to be a tech whiz to keep your emails secure. With a few basic commands, you can create an SPF record that will help protect your emails from malicious actors.