I've found several threads related to this, but they are all very dated so I want to get some clarification.
I use an AWS ec2 instance with an elastic-ip, I've set up an SMTP (sendonly) mail-server using postfix on ubuntu 18.04, and I manage my DNS through domains.google. I'm setting up all my MX, SPF, dmarc/dkim records, but I'm confused in how I set up my PTR record.
When I select "PTR", it asks for a host-name and a data-field. Here is my confusion:
The PTR record is considered a reverse-DNS no? Shouldn't it be an IP address which points to my smtp.mydomain.com? When I type the IP address in the host-name field, it appends .mydomain.com so it looks something like:
###.###.###.###.mydomain.com -> smtp.mydomain.com
Should it not just be:
###.###.###.### -> smtp.mydomain.com?
Best Answer
PTR is managed by the owner of the IP. You will need to talk with Amazon about it. The public IPv4 address you are using needs to be an Elastic IP though.
https://aws.amazon.com/blogs/aws/reverse-dns-for-ec2s-elastic-ip-addresses/