What is SPF (Sender Permitted From)?

There are many theories no how to protect agains spam....SPF is one of these.

According to the SPF home page it:

* reduces email address forgery

* and makes it easier to identify spams, worms, and viruses

* when domain owners designate sending mail exchangers in DNS, so that

* SMTP servers can distinguish legitimate mail from spam

* by verifying the envelope sender domain against client IP

* before any message data is transmitted.

The site goes further to say:

SPF was originally designed to prevent joe-jobs. In this mode, an MTA uses SPF to verify the envelope sender (SMTP MAIL FROM) address during SMTP time. But some people pointed out that SPF can also be used to verify headers to prevent phishing. When used to verify headers, the agent could be an MTA or an MUA, and slightly different rules apply: you have to consider Sender and Resent-From as well as just the "From:" header.

You can make your own mind up by going to the SPF home page.