SPF Overview

You can help eliminate the spam problem by making it easy to detect forgeries. Protect your e-mail address reputation with a simple DNS technique.
Why Do People Use SPF?

Big domains, including ISPs, banks and well-known brands care about controlling their trademarks. They have an obligation to protect their names. Altavista.com publishes an SPF record as do AOL and Oxford. More domains get on the bandwagon every day. Smaller domains publish SPFs simply because they don't want to be joe-jobbed.

On the receiving end, ISPs upgrade their MTAs and turn on SPF simply because it means less forgery—less spam, worms and viruses. Their bandwidth costs go down, too, because SPF lets them cut off the spammer before data is transmitted. They don't have to perform any cryptography or verify any signatures. SPF saves money.


By the time this article is published, SPF support should be either bundled in or available as a downloadable plugin for the latest versions of SpamAssassin, Postfix, Sendmail, Exim and qmail. Commercial antispam vendors have committed to support SPF; Declude JunkMail, for one, reports that SPF is successfully blocking spam in the field.

If all goes well, the SPF standard will be published as an RFC in the near future. But thousands of domains, including some quite large ones, already publish SPF records. There's no reason to wait; you should publish SPF today.

Meng Weng Wong is founder and CTO of pobox.com, the e-mail-forwarding company, which celebrates its tenth anniversary this year. He is working on a science-fiction novel set on a planet where traditional fantasy magic turns out to be implemented, following Clarke's famous dictum, using nanotechnology.



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Re: SPF Overview

Anonymous's picture

I read this article after reading the May 2004 article because my subscription just started up. So, interestingly, everything seemed to flow. Thank goodness Linux Journal posts their articles!

I found this one here because I read the other article and thought "Hey, I need to do/learn this! Where's that previous article." A few clicks later, there it was. :)

I can understand the first person's frustrational comment about the definition of SPF. I explained a little of what I was doing to my signifigant other, and the initial response, after defining SPF, was "Oh, I thought it was like sunblock. You know, like SPF-15, SPF-45.."

In a way, it is like sunblock. It prevents your systems from burning up from processing all of that spam!

Re: SPF Overview

Anonymous's picture

Just for the record, the other half of this article, which is obviously more detailed due to the complexity (setting up the email side of thigns), is in the April issue:



Anonymous's picture

I don't believe this article even once tells us what SPF stands for.* Perhaps it means nothing, the latest fad in (non-) acronyms.

How did this piece make it past an editor?

*For the frustrated reader: it stands for Sender Policy Framework.

Re: SPF?

Anonymous's picture

You seem to be in the possession of Internet access... A quick trip over to spf.pobox.com would have answered your question rather quickly ;)

Re: SPF?

Anonymous's picture

I think you are missing out on some experience when it comes to technical writing. Technical lingo should be explained, but not to the depth of the PDR (Physician's Desk Refeence). Because the industry is so acronym-laden, many have found a common style to use the acronum once and place an explanation in parantheses afterwards, describing the acronym or term, but after that, to use the acronym (only) as the meaning has been explained. The initial reference can be seen in my reference to the PDR above.
And finally, but most importantly, material should be written|developed|edited so a reader doesn't have to read a sentence more than once for comprehension. Have you ever found yourself halfway into a sentence (technical, romance, etc. and say, "Huh?" then go back to the beginning of the sentence and start reading it again? That's an example of a bad book. Bad book! Bad bad book.

Re: SPF?

Anonymous's picture

I agree. Thanks for suppling the definition. I though the article was good.

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