Finding: No Reverse DNS
This finding means the IP address your domain resolves to has no reverse DNS (PTR) record pointing back to a hostname. It is an email-deliverability hygiene gap, not a vulnerability.
Last updated August 11, 2026.
What it means
Forward DNS resolves a hostname to an IP address. Reverse DNS is the opposite direction: given an IP address, a PTR record answers with a hostname. Nivaronix looked up the IP your domain resolves to and found no PTR record answering for it.
Why it matters
Reverse DNS matters almost entirely for outbound email. Many receiving mail servers check that the IP a message arrives from has a PTR record, and often that the PTR hostname itself resolves back to the same IP (forward-confirmed reverse DNS). A server sending mail with no PTR record looks more like a compromised or unmanaged machine to spam filters, which can mean lower deliverability or mail landing in spam — even when SPF and DMARC are configured correctly. If this IP never sends email directly (for example, it only serves web traffic behind a managed mail provider), this finding has little practical effect.
What Nivaronix checks
After resolving your domain to an IP address, Nivaronix performs a reverse lookup on that IP. This finding fires when the lookup completes but returns no hostname for the address.
Example evidence (illustrative — not live scan data)
IP: 203.0.113.42 -> reverse lookup returned no hostname
How to fix it
- Identify who controls the IP address — usually your hosting provider or cloud platform, not your DNS host. PTR records are set on the network that owns the IP block, not in your domain's own DNS zone.
- Open a support ticket or use your provider's control panel to request a PTR record for the IP, pointing to a hostname you control (commonly the server's own hostname, such as
mail.example.com). - If this server sends mail, also create a matching A record for that hostname pointing back to the same IP, so the PTR resolves forward and back consistently.
How to verify the fix
Re-run the DNS security checker and confirm it now reports a hostname for your IP.