Requirement for rDNS

Hi,

I have setup an Exchange server on an instance. All working fine, except I cannot send to external email.
After sending this form back to AWS: https://aws-portal.amazon.com/gp/aws/html-forms-controller/contactus/ec2-email-limit-rdns-request
I received the following email:
The mapping for this reverse DNS entry is failing because the PTR record doesn't match the A record for that domain. We currently require the forward A record to match the PTR record for all reverse DNS entries.

You can either provide us with an alternate hostname, or configure the A record for this domain to match the desired PTR record on your side.

I am a bit stuck as I am not sure I understand what is required.
I have the following entries in Route 53:
MyDomain MX 10 mail. MyDomain
ns-1764.awsdns-28.co.uk.
MyDomain NS ns-1244.awsdns-27.org.
ns-828.awsdns-39.net.
ns-247.awsdns-30.com.
MyDomain SOA ns-1244.awsdns-27.org. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400
MyDomain TXT "v=spf1 mx ip4:publicIP ip4:10.44.128.0/25 -all"
Mail.MyDomain A x.x.x.x (PublicIP)

Is what AWS requesting just a new A record with the public IP pointing to MyDomain instead of mail.MyDomain?

Thanks