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PTR (Reverse DNS) lookup
Look up the PTR (reverse DNS) record for an IPv4 or IPv6 address. It is one of the fundamental signals for mail server deliverability: if the sending IP has no valid PTR, your emails may end up in spam.
About PTR Records
A PTR (Pointer) record is the DNS record that maps an IP address to a hostname. It is the inverse of an A record: A records resolve hostname → IP, while PTR resolves IP → hostname.
PTR is critical for mail servers: most major providers (Gmail, Microsoft) expect the sending IP to have a PTR record that, when resolved forward again, points back to the same IP (FCrDNS — Forward-Confirmed reverse DNS). Otherwise delivery rates drop or connections get rejected.
Importance of PTR Records
- Mail Deliverability
Mail servers without PTR are rejected by most providers.
- FCrDNS Verification
Matching forward and reverse DNS proves sender trustworthiness.
- Network Diagnostics
Explains who an IP belongs to in traceroute and log analysis.
- Spam Prevention
PTR/A mismatch raises spam scores at most providers.