PTR is set by the provider, on the IP. Not in Cloudflare.
Gmail defers mail when the reverse name is missing or does not match the name the server uses. We request the record and align the hostname. We cannot write it ourselves.
The IP, the PTR, the HELO, the A record
One hostname, usually mail.example.com or the server name. It needs an A record to this IP before the provider will accept the PTR. An orange-clouded name is the wrong target.
Hetzner, OVHcloud, Netcup and the others have a form or a panel field. We file it from your account, or tell you the exact value if you prefer to click it.
Exim or Postfix must greet with that name. A default hostname of the cloud image fails the check even after the PTR is right.
A listed IP stays listed
Reverse DNS is a prerequisite. It does not clear Spamhaus, and it does not replace SPF. If the provider will not set a PTR on that product, the practical fix is a new IP or an external sender. We say which.
€55 an hour. The provider’s approval is not on our clock.
Minimum 1 hour for the check, the A record and the request. Waiting for their panel to publish the PTR is not billed.
New IP, and mail deferred for a missing PTR?
Tell us the provider and the hostname you want. No mailbox password in the first message.