Reverse DNS Lookup
Find the hostname (PTR record) associated with an IP address. Useful for verifying mail server identities and investigating unknown IPs.
What is reverse DNS?
Reverse DNS looks up the hostname associated with an IP address — the opposite of normal DNS. It works through PTR records stored in in-addr.arpa zones. For example, 8.8.8.8 resolves to dns.google. Not all IPs have PTR records — it requires the IP owner to configure them.
Why reverse DNS matters for email
Mail servers check PTR records on connecting IPs as an anti-spam measure. If your mail server IP has no PTR record, or if the PTR doesn't match your forward hostname (FCrDNS), many receivers will reject or flag your email. Correct reverse DNS is essential for reliable email delivery from your own server.
Setting up reverse DNS
Unlike forward DNS, reverse DNS must be configured by whoever owns the IP — typically your hosting provider. For cloud servers, set PTR records in your provider's panel. For AWS, update Elastic IP settings. For DigitalOcean, rename your droplet to match the desired hostname. For ISP-allocated IPs, contact their support.
Reverse DNS for security
Reverse DNS lookups help identify unknown IPs in server logs. Googlebot has PTR records pointing to googlebot.com — you can verify legitimacy by confirming forward DNS of that hostname points back to the same IP (FCrDNS). IPs with no PTR records warrant closer investigation.