SPF Records stand for Sender Policy Framework. 

Have you ever gotten spam from yourself? I have, and I've been thinking hard about how to stop it! I didn't send it. It came from a spammer. If we could stop spammers from forging mail, we could easily tell spam from ham and block the bad stuff.

SPF makes it easy for a domain, whether it's an ISP, a business, a school or a vanity domain, to say, "I only send mail from these machines. If any other machine claims that I'm sending mail from there, they're lying."

When an AOL user sends mail to you, an email server that belongs to AOL connects to an email server that belongs to you. AOL uses SPF to publish the addresses of its email servers. When the message comes in, your email servers can tell if the server on the other end of the connection belongs to AOL or not.

And that's it!

SPF aims to prevent spammers from ruining other people's reputations. If they want to send spam, they should at least do it under their own name.

And as a user, SPF can help you sort the good from the bad. Reject mail that fails an SPF check. Use it to help your spam filters make a decision. Have confidence that mail that SAYS it's coming from your bank, your credit card company, or the government really is!

If you do get spam that passed an SPF check, then you know you should hold the sending domain responsible for the message.