Email delivery delayed or not received

We just changed to Windows Small Business Server and although email is up and running, we are getting messages that email delivery has been delayed for AOL and comcast.net reciepients. I believe this to be due to the SPF DNS entry. Although we have one, testing it has indicated that it can not be seen outside our seperate ISA firewall.

What can be done to get this SPF record published to the internet?