Sender Policy Framework

What does the logo mean?

You're looking at an envelope. The return address claims to be from Blue Blob. Let's compare that to the postmark. Yup, the postmark says the message comes from Blue Blob. That means the return address is probably not made up. The message is good.

In e-mail, the envelope sender, also known as the return-path, is the return address. The SMTP client is the post office that applied the postmark. The blue blob is the domain name. If they don't match, maybe the message is a forgery. Maybe a bad guy made up the return address to fool you into opening the envelope. Maybe a spammer forged a Paypal return address to try to get your credit card number.

You can display the SPF logo on your website. Choose one that's right for you.