We are hosting our site on an Ec2 instance. Our Elastic IP is w.x.y.z and Public DNS is: ec2-w-x-y-z.compute-1.amazonaws.com.

We've bought a domain name domainname.com from a lesser known domain-name-seller. We added an A-record pointing domainname.com to w.x.y.z. Will this work or do we need a CNAME record to point to the same too?

We wanted to use Google apps for emailing so adjusted the TXT/MX records according to the Google Apps instructions to be able to send/recv email using @domainname.com email addresses.

Have we got it right, more important, we came across queries relating to email sent from ec2-w-x-y-z.compute-1.amazonaws.com (our users can send email from their onsite accounts) going to spam (rDNS not pointing to domainname.com but to ec2-w-x-y-z.compute-1.amazonaws.com). How can we fix this? We came across SPF records, do they provide a complete solution? We aren't sure as to how to use them. Can you help pls?

Thank you, Sid