How do you setup an SPF Record?
First, go to: http://www.anti-spamtools.org/ and use the Online Wizard (we've found this to be the best way) and you should get something like below:
Example: v=spf1 a mx ptr ip4:220.127.116.11 mx:mail.scarletts-web.com ip4:18.104.22.168 -all
Then go to SiteWorx > Domains > DNS Records > and click View Records next to the domain.com.
Add a TXT record and paste what you copied into the Text field.