(FAQ) What is SPF?
SPF (Sender Policy Framework) is an anti-spam approach which compares the Internet domain of an email-sender to a list of valid IP addresses which may send mail on behalf of that domain. This practice discourages spammers that routinely disguise the origin of their email – a practice commonly known as email spoofing. SPF and other anti-spoofing initiatives, such as Domain Keys, work by making it easier for a mail server to determine when a message came from someone unauthorized to send mail from a specific domain.
For more information on SPF and assistance setting up your SPF records please go to http://spf.pobox.com.