Reverse DNS Lookup (PTR)
Find the hostname behind any IP address. Essential for email deliverability and network diagnostics.
Popular checks: 8.8.8.8 · 1.1.1.1 · 208.67.222.222
📖 What is Reverse DNS?
Reverse DNS (rDNS) maps an IP address back to a hostname using PTR records — the opposite of forward DNS (A/AAAA records). It's stored under the special domain .in-addr.arpa (IPv4) or .ip6.arpa (IPv6).
Why it matters: Most email servers (Gmail, Outlook, Yahoo) perform rDNS checks on incoming connections. If your mail server's IP doesn't have a matching PTR record, your emails are more likely to land in spam or be rejected outright.
Forward-confirmed reverse DNS means the PTR record's hostname also has an A record pointing back to the original IP. This is the gold standard for email deliverability.