Networking
What is Reverse DNS?
Reverse DNS maps an IP address back to a hostname through a PTR record, the inverse of a normal DNS lookup. It is effectively mandatory for outbound mail: most large receivers reject messages from addresses whose PTR does not resolve back to the sending hostname.
Why Reverse DNS matters
It is effectively mandatory for outbound mail: most large receivers reject messages from addresses whose PTR does not resolve back to the sending hostname.
Reverse DNS in practice
When you're running a mail server, reverse DNS is the PTR record on your IP address. You set it in the panel, point it at a hostname that resolves back to the same IP. Receivers check it on every inbound message. Get it wrong or leave it missing and your mail lands in spam or gets rejected outright. For anything else, it barely matters, but for mail it's the difference between delivery and silence. You'll also see it when troubleshooting: a missing PTR often explains why a connection is refused.
What people get wrong about Reverse DNS
The common mistake is thinking reverse DNS is just a hostname lookup in the other direction. It isn't. Forward DNS is authoritative for names; reverse DNS is authoritative for IPs, and they're separate zones. A mismatch — where the PTR points to a hostname that doesn't resolve back — is worse than no PTR at all. Set them to match exactly.
Reverse DNS — common questions
What happens if I don't set a PTR record?
If you run a mail server, most large receivers reject messages from addresses without a valid reverse DNS match. Your mail gets bounced or spam-filtered. For web or VPN traffic, it rarely matters. But if you plan to send mail from that IP, set the PTR before you start.
How do I set a reverse DNS record?
In your OnionVPS panel, find the IP address for your server, enter the hostname you want the PTR to resolve to, and save. It propagates within minutes. Ensure that hostname has a forward A record pointing back to the same IP, or the PTR won't be considered valid by strict receivers.
Where Reverse DNS comes up
- What is included in every plan? Full root access, KVM virtualisation with custom kernel support, custom ISO upload, an out-of-band VNC console, one IPv4 address, a routed IPv6 /64, always…
- Can I set reverse DNS (PTR) records myself? Yes, for both IPv4 and IPv6, directly from the control panel, and changes propagate within minutes. Reverse DNS is essential for mail: most large receivers…
- Can I run my own mail server on a VPS? Yes. Port 25 is open, reverse DNS is self-service, and our address space has no spam history. Mailcow or Stalwart give you a complete stack in an evening. …
- A self-hosted mail server that actually reaches the inbox Installing a mail server is easy; being trusted by receivers is not. You need outbound port 25, a PTR record matching your banner hostname, SPF, DKIM and D…
- Is outbound port 25 open, so I can run a mail server? Yes, outbound port 25 is open on every OnionVPS instance by default. There is no support ticket, no account-age requirement and no paid unblock. Most provi…
- What makes OnionVPS different from other VPS providers? Four things: no identity verification of any kind, crypto-only payment with no card or bank involved, 138 locations in 116 countries including genuine offs…
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