What is SPF record? What do I need to do about it?

Due to the fact that a significant majority of SPAM comes from forged addresses, a new Sender Policy Framework (SPF) standard is being implemented by a number of ISPs and mail hosts, including several major providers (Hotmail, Yahoo, AOL, etc). Those providers have begun to require SPF to allow mail through their networks. Mail systems will need SPF records for their domains if they want their mail to be accepted by those providers.