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    Reverse DNS Configuration

    Set up PTR records for email deliverability and server legitimacy

    Overview

    Reverse DNS (rDNS) maps an IP address back to a domain name. It's particularly important for mail servers and helps establish legitimacy for various services.

    Why is Reverse DNS Important?

    Email Deliverability

    Many mail servers require matching forward and reverse DNS

    Spam Prevention

    Proper rDNS helps prove you're a legitimate sender

    Professional Appearance

    Shows proper server configuration

    Logging & Monitoring

    Makes log files more readable with domain names

    Setting Reverse DNS

    Step 1: Navigate to Networking

    1. Log into the Cloud Control Panel
    2. Select your instance from the Instances tab
    3. Click on the Networking tab

    Step 2: Configure rDNS

    1. Find your IP address in the list
    2. Click the edit icon next to the IP address
    3. Enter your desired hostname (e.g., mail.example.com)
    4. Click Save

    Reverse DNS Requirements

    For reverse DNS to work properly:

    • You must own or control the domain name you're setting
    • Forward DNS (A record) must already be configured for the hostname
    • The forward DNS should point to the same IP address
    • Hostname should be a fully qualified domain name (FQDN)

    Verifying Reverse DNS

    After setting reverse DNS, you can verify it's working:

    Linux/Mac

    # Check reverse DNS
host YOUR_IP_ADDRESS

# Or use dig
dig -x YOUR_IP_ADDRESS

    Windows

    nslookup YOUR_IP_ADDRESS

    DNS Propagation

    DNS changes can take time to propagate. Wait at least 30 minutes to an hour before checking. Some DNS servers cache records longer.

    Email Server Configuration

    If you're running a mail server, proper rDNS is essential:

    Setup Steps

    1. Set up forward DNS (A record) for your mail hostname
    2. Set up reverse DNS (PTR record) pointing back to the same hostname
    3. Ensure they match exactly
    4. Configure your mail server's HELO/EHLO hostname to match

    Example Configuration

    Forward DNS:

    mail.example.com. IN A 198.51.100.10

    Reverse DNS:

    10.100.51.198.in-addr.arpa. IN PTR mail.example.com.

    MX Record:

    example.com. IN MX 10 mail.example.com.

    Best Practice

    Always set reverse DNS for any server that sends email. Many mail servers will reject or mark as spam emails from IPs without proper rDNS configuration.