PTR Records

Reverse DNS (rDNS) - IP address to domain name mapping

PTR Records Properly Configured

All your mail server IP addresses have valid PTR records pointing back to your domain. This improves email deliverability.

What are PTR Records?
PTR (Pointer) records provide reverse DNS lookups, mapping an IP address back to a domain name. They're essential for email servers and network diagnostics.
Why is it important?
Many email servers check PTR records to verify legitimate senders. Missing or incorrect PTR records can cause your emails to be rejected or marked as spam.
Impact
Without valid PTR records, your email deliverability suffers significantly, and some mail servers may automatically reject your messages.

Detected PTR Records

IP AddressPTR RecordStatusMatchLast Checked
192.0.2.1
Mail Server (Primary)
mail.example.comValidForward Match ✓2 hours ago
192.0.2.2
Mail Server (Backup)
mail2.example.comValidForward Match ✓2 hours ago
2001:db8::1
IPv6 Mail Server
mail.example.comValidForward Match ✓2 hours ago

Configuration Details

Forward DNS vs Reverse DNS

Forward DNS
Domain → IP

Resolves domain names to IP addresses. This is the normal DNS lookup process.

mail.example.com → 192.0.2.1
  • User types domain name
  • DNS returns IP address
  • Browser connects to IP
Reverse DNS (PTR)
IP → Domain

Resolves IP addresses back to domain names. Used for verification and security checks.

192.0.2.1 → mail.example.com
  • Server receives connection from IP
  • Performs reverse DNS lookup
  • Verifies hostname matches

How to Configure PTR Records

  1. Important: PTR records must be configured by your IP address provider (hosting provider, ISP, or data center), not your domain registrar.
  2. Contact your hosting provider's support team or access their control panel.
  3. Navigate to the reverse DNS or PTR record management section.
  4. For each mail server IP address, create a PTR record pointing to your mail server hostname:
    192.0.2.1 → mail.example.com
  5. Ensure your forward DNS (A record) matches:
    mail.example.com → 192.0.2.1
  6. For IPv6 addresses, create AAAA and corresponding PTR records:
    2001:db8::1 → mail.example.com
    mail.example.com → 2001:db8::1
  7. Wait for DNS propagation (typically 1-24 hours).
  8. Verify your PTR records using command line tools:
    # Linux/Mac
    dig -x 192.0.2.1
    nslookup 192.0.2.1

    # Windows
    nslookup 192.0.2.1

PTR Record Format

PTR records use a special reverse notation for IP addresses:

IPv4 PTR Record:

IP: 192.0.2.1 becomes 1.2.0.192.in-addr.arpa

1.2.0.192.in-addr.arpa. IN PTR mail.example.com.
IPv6 PTR Record:

IP: 2001:db8::1 becomes nibble format

1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa. IN PTR mail.example.com.

Common PTR Record Issues

PTR Record Best Practices