Editing Sender Policy Framework (section)

===Mechanisms===
Eight ''mechanisms'' are defined:
{|
| valign="top" | ALL || Matches always; used for a default result like <code>-all</code> for all IPs not matched by prior mechanisms.
|-
| valign="top" | A || If the domain name has an address record (A or AAAA) that can be resolved to the sender's address, it will match.
|-
| valign="top" | IP4 || If the sender is in a given [[IPv4]] address range, match.
|-
| valign="top" | IP6 || If the sender is in a given [[IPv6]] address range, match.
|-
| valign="top" | MX || If the domain name has an [[MX record]] resolving to the sender's address, it will match (i.e. the mail comes from one of the domain's incoming mail servers).
|-
| valign="top" | PTR || If the domain name ([[PTR record]]) for the client's address is in the given domain and that domain name resolves to the client's address ([[forward-confirmed reverse DNS]]), match.  This mechanism is discouraged and should be avoided, if possible.<ref name="rfc7208-txt" />
|-
| valign="top" | EXISTS || If the given domain name resolves to any address, match (no matter the address it resolves to). This is rarely used. Along with the SPF macro language it offers more complex matches like [[DNSBL]]-queries.
|-
| valign="top" | INCLUDE || References the policy of another domain. If that domain's policy passes, this mechanism passes. However, if the included policy fails, processing continues. To fully delegate to another domain's policy, the ''redirect'' extension must be used.
|}