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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.
This page is the full reference: every mechanism, every qualifier, both modifiers, the complete macro table, evaluation order, DNS lookup limits, and record placement rules — each with the RFC 7208 section that defines it. If you want protocol fundamentals first — why SPF exists and how it fits with DKIM and DMARC — start with our SPF guide. If you build and maintain records, bookmark this.
SPF Record Syntax at a Glance
An SPF record is one string of text in the RDATA of a single TXT record, and its grammar has exactly three kinds of parts: a version tag, mechanisms (each with an optional qualifier), and modifiers. The version tag must be exactly v=spf1 — a record starting v=spf10 is discarded, not partially matched (§4.5).
Every SPF record is the same three kinds of parts: a version tag, mechanisms with optional qualifiers, and modifiers.
The grammar in brief, from §3 and §4.6.1:
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