Setting up a SPF record is pretty easy. You can follow the steps that i have listed below:
- Provision an Elastic IP for your server
- Setup an "A" record for the server which will be sending mail with your preferred registrar
- Contact amazon and ask for a reverse dns record for the IP.
- Add the following somewhere in your SPF record and you should be good to go: app-svr-01.youdomain.com
Note: If you need to relay mail through this server from your other AWS servers, or communicate between servers in any other way, you should not use this new FQDN, but use the AWS FQDN from the AWS console (it will look like ec2-xxx-xxx-xx-xx.compute-1.amazonaws.com).