Glossary
Email authentication
Modifier
An SPF term that changes evaluation rather than matching an IP — redirect and exp. A modifier may appear only once and is not position-sensitive the way a mechanism is.
Defined in RFC 7208 §6.
Where this appears
The lessons that use this term, and what each is for.
Email Authentication FundamentalsThe shape of an SPF recordFind a domain’s SPF record and break it into its terms.Email Authentication Fundamentalsinclude, redirect, and nested recordsTrace an SPF evaluation through nested includes and say where it stopped.SPF PractitionerThe algorithm, term by termWalk any evaluation in the order a receiver walks it, and say where it stopped.SPF Practitionerexp=, the modifier almost nobody publishesPublish a useful explanation string, and say why most domains should not bother.SPF PractitionerOne policy, many domainsUse redirect to give fifty domains one maintained record without copying it fifty times.