Sender Policy Framework

What is the price for using the spf service?

First of all, spf is not a service. It is a specification of how domain owners can publish their policy regarding the use of their domains in email traffic and a specification of how receiving mail servers should interpret this policy. It is an open standard, and thus free to use for everyone. Publishing spf records is done in your own DNS by you or your ISP or IT department. Checking for spf records on incoming mail is available as a free add-on for most main-stream mail servers like sendmail, postfix and others (with the exception of most proprietary mail servers). Many proprietary servers support SPF or have add-ons that are available. Contact your vendor for more information. See the Implementations page for more details.

If you need help from a consultant in setting up spf, take a look at this list of consultants.