Reverse DNS (RDNS / PTR Records) – Firstserv Guide
DNS (Domain Name System) allows you to map a domain or server name to an IP address. For example:
www.yourdomain.com → 123.123.123.123
DNS also supports Reverse DNS (RDNS), which performs the opposite lookup—resolving an IP address back to a hostname using a PTR (Pointer) record.
What is Reverse DNS (RDNS)?
RDNS allows a lookup like:
123.123.123.123 → server.yourdomain.com
This confirms that a specific IP address is correctly associated with a domain name.
Why RDNS is Important
RDNS is especially important if you are running an email service on your server.
When your server sends email:
- Receiving mail servers often perform an RDNS lookup
- They check that:
- The sending IP resolves to a valid hostname
- The hostname matches the domain used in the email
✅ With RDNS Configured
- Improves email deliverability
- Builds trust with receiving servers
- Reduces the likelihood of emails being marked as spam
❌ Without RDNS
- Emails may be:
- Rejected
- Marked as spam
- Some mail servers will refuse messages from IPs without valid RDNS
How to Request RDNS Setup
RDNS (PTR records) must be configured at the server level and cannot be added directly through typical DNS tools.
To set up RDNS on Firstserv:
- Log in to your Firstserv Client Area
- Open a support ticket
- Provide the following information:
Server IP address: [Your VPS or Dedicated Server IP]
Fully Qualified Domain Name (FQDN): server.yourdomain.com
What is an FQDN?
An FQDN (Fully Qualified Domain Name) is the full hostname assigned to your server.
✅ Examples:
server.example.co.uk
mail.example.com
host.yourdomain.net
Best Practice
For RDNS to work correctly:
- ✅ Ensure the FQDN has a matching A record pointing to your server IP
- ✅ Ensure the PTR (RDNS) record matches that hostname
👉 This is known as forward-confirmed reverse DNS (FCrDNS) and is essential for email reliability.
Summary
- DNS maps domains to IPs; RDNS maps IPs back to domains
- RDNS is critical for sending email from VPS or dedicated servers
- PTR records must be configured by Firstserv support
- Requires a matching hostname (FQDN) and DNS setup
Need Help?
If you need assistance setting up RDNS or verifying your configuration, the Firstserv support team is always happy to help.
WGS AI Assistant