- Sender Policy Framework.
SPF is an open standard that attempts to address spoofing of email addresses. SPF provides a standard mechanism to verify that the sending domain is permitted to send emails on behalf of that domain.
SPF records indicate which mail servers are permitted to send email with a given "from" address. SPF is an attempt to counter "e-mail address spoofing", where a sender (typically a spammer) uses someone else's e-mail address as the apparent sender of an e-mail. SPF records do not indicate that a message is not spam, as spammers can set up SPF records for their own domains, but an SPF fail does give a high confidence that an email is bogus.
For more information see: