IP Reputation Checker

Receiving mail servers check whether a connecting IPv4 address publishes a PTR record under in-addr.arpa and whether that hostname resolves back to the same IP (forward-confirmed reverse DNS). Missing or mismatched PTR records frequently trigger SMTP 421/550 deferrals or rejections before message headers are even inspected.

• Checks IPv4 reverse DNS (PTR), forward-confirmed reverse DNS (FCrDNS), and 4 public DNSBL zones (SpamCop, Barracuda, PSBL, UCEPROTECT Level 1).
• Private, loopback (except the RFC 5782 test point 127.0.0.2), and reserved IP ranges are rejected.
• Mailbox providers maintain proprietary IP reputation scores (such as Google Postmaster Tools and Microsoft SNDS) that cannot be queried anonymously.
• Anonymous use is limited to 30 checks per hour.

• Email blacklist checker
• Email deliverability test
• DNS checker
• All free email tools