SPF record
The TXT record, starting with v=spf1, that holds a domain's SPF policy: an ordered list of mechanisms and modifiers ending in a default such as -all.
What it means
An SPF record is a TXT record published at the domain being checked. It must begin with v=spf1, followed by terms read from left to right: mechanisms (ip4, ip6, a, mx, include, exists, ptr, all), each with an optional qualifier, and the modifiers redirect and exp. The first mechanism that matches decides the result.
A domain must publish only one SPF record. Two TXT records that both start with v=spf1 produce a permerror, which receivers treat as a broken record. A record longer than 255 characters is split into several quoted strings inside one TXT record, and receivers join them without spaces. RFC 7208 asks publishers to keep the whole answer small enough to fit in a 512-byte DNS response.
The dedicated SPF record type (type 99) from the experimental era was dropped by RFC 7208: only TXT counts.
Example
v=spf1 ip4:203.0.113.10 include:_spf.google.com ~allRelated terms
On this site
Sources
What this definition rests on. The wording is ours; the facts are theirs.
- RFC 7208: Sender Policy Framework (SPF), section 3rfc-editor.org
- RFC 7208: Sender Policy Framework (SPF), section 4.5rfc-editor.org
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