550 5.7.25 This message was blocked because the sending IP address doesn't have a PTR record, or the forwarding DNS entry doesn't reference the sending IP address
Sample bounce line
550 5.7.25 This message was blocked because the sending IP address doesn't have a PTR record, or the forwarding DNS entry doesn't reference the sending IP address. Gmail requires that sending IP addresses have a PTR record. Learn more about requirements for sending IP addresses. To learn more about Gmail requirements for bulk email senders, visit Email sender guidelines.
What it means
Gmail requires sending IP addresses to have a PTR record, and this one is missing or the forward DNS entry does not point back to the sending IP, so the message was blocked.
Why it happens
- The sending IP has no PTR (reverse DNS) record.
- The PTR hostname has no A (IPv4) or AAAA (IPv6) record resolving to the same sending IP.
How to fix it
- Give the public IP address of the sending SMTP server a PTR record that resolves to a hostname (reverse DNS lookup).
- Make sure the same hostname has an A record (IPv4) or AAAA record (IPv6) resolving to the same public IP used by the sending server (forward DNS lookup).
- Confirm the sending IP address matches the IP of the hostname in the PTR record.
- Ask your hosting or ISP provider to set the PTR record if you do not control the IP's reverse DNS, then resend.
DNS record examples (replace example.com and the values with your own):
203.0.113.25 -> mail.example.com (PTR, set by whoever owns the IP) mail.example.com. IN A 203.0.113.25 ; forward record must point back to the same IP
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