Life of an Admin

SMTP email allows any computer to send an e-mail claiming to be from anyone. Thus, it is easy for spammers to send e-mail from forged addresses. This makes it difficult to trace back to where the spam truly comes from, and easy for spammers to hide their true identity in order to avoid responsibility.

SPF or Sender Policy Framework, allows the owner of an Internet domain to use special format of DNS TXT records or the newer SPF records to specify which machines are authorized to transmit e-mail for that domain.

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."

So what does SPF actually do ?

Suppose a spammer forges a hotmail.com address and tries to spam you.He connects from somewhere other than hotmail.When his message is sent, you see MAIL FROM: , but you don't have to take his word for it. You can ask Hotmail if the IP address comes from their network.
Hotmail publishes an SPF record. That record tells you (your computer) how to find out if the sending machine is allowed to send mail from Hotmail.
If Hotmail says they recognize the sending machine, it passes, and you can assume the sender is who they say they are. If the message fails SPF tests, it's a forgery. That's how you can tell it's probably a spammer.

For more information on SPF, and you to create SPF records for your domains, visit
openspf.org