Reverse DNS (PTR record)
A PTR record links an IP address to a host name. Important if you send email from your own server.
A regular A record says: this name belongs to this IP address. A PTR record works the other way round: this IP address belongs to this name. This is called reverse DNS.
Why does it matter?
Receiving mail servers often check the reverse DNS of the server delivering an email. Is the PTR record missing, or does it not match the name the server introduces itself with? Then your email is more likely to end up in spam or be rejected.
For a good result, all of this must match:
- The IP address has a PTR record, for example to
mail.example.com. mail.example.comhas an A record pointing to that same IP address.- The mail server introduces itself with the name
mail.example.com.
Where do you set it?
A PTR record is not part of your domain's DNS. The owner of the IP address manages it:
- Web hosting with Knippin: already taken care of. Our mail servers have correct reverse DNS.
- VPS or server with Knippin: create a ticket with the IP address and the desired host name. First add the A record for that host name yourself via Managing DNS records.
- Server with another provider: request the PTR record from that provider.
Checking
On Windows, type nslookup 203.0.113.10 (with your own IP address) in a command prompt. On macOS or Linux, type dig -x 203.0.113.10 +short. You will see the host name that belongs to the IP address.