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Sender Policy Framework

Term: Email Server - This is a system of hardware and software that processes email messages. It handles everything from accepting new mail from sources such as your own computer to delivering email to its destination and everything in between.

Term: SMTP Server - This is a system of hardware and software used to deliver email messages to other servers.

SPF and Sender ID are both terms that refer to the use of the domain name system to establish whether or not the IP Address of the delivering SMTP server is legitimate.

It is becoming the widely accepted method for businesses to identify which IP Addresses may be used to send mail for their domains. To clarify, what it does is to help our system verify that the connecting IP is or is not a legitimate IP for a given domain.

For example, if an SMTP server connects to our equipment trying to deliver an email message for AOL.COM, we check the SPF records for AOL to see if the IP Address the delivering system is using is legitimate for AOL.

On the surface, it is hard to imagine that the delivery of email has gone this long without the implementation of such a system. Progress is being made and someday one part of the spam puzzle will be solved. It doesn't stop spam because spammers often use SPF compliant domains, but it adds a layer of protection and certainly assists with the reduction of phishing attacks. However, when used with Source Authentication the combination stops spam in its tracks.