The receiver could not confirm your sending IP with reverse DNS: the IP has no PTR record, or the PTR name does not resolve back to the same IP.
Policy rejection · fixable
Common causes
- The PTR record was never set for your server IP
- The PTR points to a generic host name of the hosting company
- The PTR host name does not resolve back to the IP (no forward confirmation)
How to fix it
- Ask your VPS or hosting provider to set the PTR of your IP to your mail host name, e.g. mail.yourdomain.com
- Create an A record for that host name pointing to the same IP
- Use the same host name in your server's HELO / EHLO greeting
PTR / Reverse DNSRun the right check for your domain or paste the full bounce message for a precise explanation.
Open PTR / Reverse DNS →Frequently asked questions
Where do I set a PTR record?
At whoever owns the IP address — usually your hosting or VPS control panel (rDNS / PTR), not at your domain registrar.