Glossary
Reverse DNS (rDNS) — What It Is and Why It Matters
Reverse DNS (rDNS) is the process of resolving an IP address back to a hostname — the reverse of a standard DNS lookup. For email, receiving mail servers perform a reverse DNS lookup on your sending IP to verify it has a valid PTR record. An IP with no reverse DNS or with a PTR that doesn't forward-confirm is a common cause of email rejection and spam folder placement.
Forward-Confirmed Reverse DNS (FCrDNS)
A valid reverse DNS setup requires both steps:
- IP → PTR lookup → hostname
- Hostname → A lookup → same IP
If step 2 returns a different IP, the check fails even though a PTR exists.
Who Controls rDNS
Your hosting provider or ISP — not your domain registrar. Set it in your VPS control panel.
Check PTR with your sending IP
Open DNS Preflight →FAQ
What is reverse DNS?
The process of resolving an IP address back to a hostname using a PTR record. Mail servers use this to verify your sending infrastructure.
Why does reverse DNS matter for email?
Many mail servers reject email from IPs with no PTR record or where the PTR hostname doesn't forward-resolve to the same IP.
Who sets up reverse DNS?
Your hosting provider or ISP — not your domain registrar. Look for "Reverse DNS" in your VPS control panel.