What is reverse DNS (PTR) and why mail servers need it
A normal DNS lookup turns a name into an IP address. Reverse DNS does the opposite: it turns an IP address into a name, using a PTR record.
Why mail servers care
Many receiving servers check that the IP address connecting to them has a PTR record, and that the name it points to resolves back to the same IP. A missing or generic PTR is a common reason for mail being rejected or sent to spam.
Who sets it
The PTR record belongs to whoever owns the IP address, usually your hosting provider. You ask them to set it, and they typically want to know the hostname and see that you run a legitimate service.
A simple checklist
- Pick a hostname such as mail.example.com.
- Create an A record from that hostname to the server IP.
- Ask the provider to set the PTR for the IP to the same hostname.
- Use the same name in your mail server's HELO/EHLO greeting.
- Configure SPF, DKIM and DMARC.
Our KumoMTA + Listmonk setup includes this checklist.