What Is Reverse DNS (PTR Record)?
Explanation of reverse DNS (PTR record) — why it matters for email delivery, how to configure it and how to check it.
What Is Reverse DNS?
Reverse DNS (rDNS) is the opposite of regular DNS: instead of translating domain → IP, it translates IP → domain name. This is done via a special DNS record type called a PTR record (Pointer Record).
Example:
- Forward DNS:
mail.example.com → 203.0.113.10 - Reverse DNS:
203.0.113.10 → mail.example.com
Why Does Reverse DNS Matter?
For Email Delivery
This is the primary reason you need a correct PTR record. Before accepting your email, a mail server checks:
- Does the sender's IP have a PTR record?
- Does the hostname returned by PTR resolve back to the same IP (forward-confirmed rDNS)?
- Does the PTR hostname match what the server uses in HELO/EHLO?
If any of these fail, many mail servers automatically reject the email or mark it as spam.
For Logging and Monitoring
In logs you see hostnames instead of cryptic IPs: mail.example.com instead of 203.0.113.10. Much more useful for debugging.
For Network Tools
Tools like traceroute, whois and ping display hostnames instead of IPs when a PTR record exists.
How to Set Up a PTR Record
- Find who controls your IP — check your VPS/dedicated server control panel. There's usually a "Reverse DNS" or "PTR record" option.
- Set the PTR value — the hostname you set must resolve back to the same IP (forward-confirmed). If you set
mail.example.com, thenmail.example.commust have an A record pointing to that IP. - Wait for propagation — PTR changes typically take 1–4 hours.
Example of correct setup:
A record: mail.example.com → 203.0.113.10 PTR record: 203.0.113.10 → mail.example.com
This bidirectional mapping is called FCrDNS (Forward-Confirmed Reverse DNS) and is what mail servers verify.
Check PTR records and DNS entries for any IP or domain:
→ DNS CheckerHow to Check Your PTR Record
From the command line:
dig -x 203.0.113.10 # dig reverse lookup nslookup 203.0.113.10 # Windows/Linux host 203.0.113.10 # Linux
Or use NerdTools DNS Checker — select record type PTR and enter the IP in reversed octets format (e.g. for 203.0.113.10 → 10.113.0.203.in-addr.arpa).
Shared Hosting — What Happens?
On shared hosting, the IP belongs to the hosting provider and serves many domains. Your hosting's PTR record likely points to the provider's hostname (e.g. mail.hostingprovider.com), not your domain.
This can negatively affect email delivery — if you have issues, the solution is to use an external mail provider (Google Workspace, Brevo, Mailgun, etc.) instead of sending email from shared hosting.