Reverse DNS (PTR record) maps an IP address to a hostname. It matters above all for mail servers: many receiving servers check whether name and address match. With cloud servers you set it yourself for every assigned address - IPv4, IPv6 and additional IPs.
How to proceed
- In the DNS zone of your domain, create an A record (IPv4) or AAAA record (IPv6) pointing to exactly this IP address, for example
mail.muster.de → 203.0.113.10. Wait until the record resolves. - In the Overview tab, in the IP addresses card, open the pencil Edit reverse DNS next to the address.
- Enter the fully qualified hostname and click Save.
When saving, we check whether the name really points to the address (forward-confirmed reverse DNS). If it does not, a message with the reason appears. The entry is then shown as Pending briefly until our network provider has taken it over, and then as Set.
Restore default resets the name to our default value or removes it if there is none. An empty field has the same effect. More than 10 changes per minute are rejected.
For mail servers
Use the same name for reverse DNS as your mail server announces itself with (HELO), and additionally set up SPF, DKIM and DMARC for your domain.
The message says the name does not point to the address.
dig +short mail.muster.de. After a change it may take a while, depending on the TTL, until the new value applies everywhere.