httpwebwitch - 3:00 pm on Sep 16, 2011 (gmt 0)
Take heed: this SPF stuff requires that you change the DNS records for your domain. If you're familiar with DNS and how it works and how to change it without breaking everything, then all is well. But if you're new to DNS shenanigans, it's good to do a little reading & refresher before fiddling with it.
The SPF record has a type "TXT". Some of my servers are running WHM - and with that I'm able to add a "TXT" records to the DNS, no problem.
But I also have a couple of Rackspace Cloud instances, and using their management tool you can add an "A", "CNAME", "MX", but... not a "TXT". To add an SPF record to a Rackspace VPS, you have to open a support ticket and get one of their support staff to do it for you.