Sender Policy Framework

Sender Policy Framework or SPF for short is a way to tell the world which mail servers that are allowed to send mail from a domain.

You can read an introduction to Sender Policy Framework at the SPF Project site.

If you use Google Apps to handle the mail for your domain they have information in their help pages about the correct SPF record to set for your domain. Note, however, that you have to use “-characters around the string to get it published as one string and not as three different strings.

Once you’ve made the changes to the DNS record you can verify if the SPF information is set correctly by using these SPF Record Testing Tools.