SpamAssassin Rule: SPF_PASS
Standard description: SPF: sender matches SPF record
SPF (Sender Policy Framework) is an open standard specifying a technical method to prevent sender address forgery. The sender's domain is matched against a list of allowed mail relays for that domain. This states, for example, that mail from firstname.lastname@example.org should have come via mail.example.com and not mail.badguys.info.
This often breaks where users have forwarded their email to another domain, but the forwarding mechanism is not SPF-aware. Such a user would see SPF_FAIL tags on some of their incoming mail.
A "Pass" result means that the client is authorized to inject mail with the given identity. The domain can now, in the sense of reputation, be considered responsible for sending the message. Further policy checks can now proceed with confidence in the legitimate use of the identity.
From RFC 4408
The default scores for this rule can be found in the online list of tests.