Sender Policy Framework(SPF) - by DNSEXIT.com
What is SPF?
SPF fights email address forgery and makes it easier to identify spams, worms,
Domain owners identify sending mail servers in DNS TXT Records.
SMTP receivers verify the envelope sender address against this information, and can distinguish legitimate mail from spam before any message data is transmitted.
More about SPF
The SPF home page, located at http://spf.pobox.com, is recommended reading. You may want to review their FAQ, the Executive Summary, or join the SPF mailing list.
Using SFP with DNS-EXIT
Our first phase in the rollout of SPF support is to add TXT DNS records to your DNS interface. SPF data is published in these TXT records.
TXT Section is hidden by default, you will need to enable TXT records in the Domain Settings section:
Our TXT record data can be any string less than 200 characters, all double-quotes are escaped with a backslash, and all non-ASCII characters are converted to %xx, where "xx" is the hexadecimal code for that character.
Once you have TXT records enabled for your domain, you will need to generate SPF data for your domains. The easiest way to do this currently is by using the SPF Publisher Wizard on the SPF homepage.
When you have generated SPF data for your domain, copy that information and enter it into a TXT record for your root domain in your DNS settings.
Make Sure It Works
You can test your SPF records using a third party-utility at one of these sites:
SPF Standard Reference