SPF Record Syntax: Mechanisms, Qualifiers, Modifiers, and Macros
This article provides a comprehensive technical reference for SPF (Sender Policy Framework) record syntax. It details the mechanisms, qualifiers, and modifiers required to properly configure DNS TXT records for email authentication.
Why it matters
Proper SPF configuration is critical for preventing email spoofing and ensuring high deliverability for domain owners.
SPF Record Syntax: Mechanisms, Qualifiers, Modifiers, and Macros SPF record syntax follows one shape: a single DNS TXT record that starts with v=spf1 , followed by space-separated terms — mechanisms with optional qualifiers, then modifiers — evaluated left to right until the first match. Here is a complete record:
v=spf1 ip4:192.0.2.0/24 include:_spf.example.com -all That one line authorizes a /24 network and a third party’s servers, then fails everything else. Every rule governing it lives in RFC 7208 , the SPF standard published in April 2014.
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