Mail Domain Check
Email sending infrastructure
Reverse DNS and PTR checker
Test an actual outbound IPv4 or IPv6 address for a PTR record and confirm that its hostname resolves forward to the same IP.
INPUT
Outbound sending IP
Use the address that actually connected to the recipient, usually shown in brackets in the complete SMTP rejection. Website and MX addresses can be different.
RESULT
Forward-confirmed reverse DNS
Enter the exact public outbound address to compare its reverse PTR answer with its forward A or AAAA result.
- IP version
- PTR records
- Forward type
- Forward addresses
- Queries completed
- Forward confirmed
The free result omits PTR hostnames, raw DNS answers, and remediation actions. A passing DNS pair does not establish IP reputation or guarantee delivery.
Forward-confirmed reverse DNS
A PTR record alone is only half of the check
The reverse zone should return a stable hostname for the actual public SMTP sending address.
At least one forward address must equal the original IPv4 or IPv6 address.
Google documents both a missing PTR and a forward entry that does not reference the sending IP as blocking conditions.
Primary references: Gmail SMTP errors, Google email sender guidelines, and RFC 1912.