VPSCryptoWhat is reverse DNS?
Forward DNS turns names into addresses; reverse DNS turns an address back into a name via a PTR record. It is the first credential a mail gateway checks — and on a VPS it is set by your host, not your registrar.
Updated 2026-06-12
DNS you know runs forward: mail.example.com → 203.0.113.7. Reverse DNS runs the other way: a query for 7.113.0.203.in-addr.arpa returns a PTR record naming the host. Because PTR records live in zones delegated along with the IP space itself, only whoever controls the address block — your hosting provider, not your domain registrar — can publish them. That obscure plumbing has one famous consequence: email. Receiving gateways treat the PTR as a first-pass honesty check, and a missing or generic one (static-1-2-3-4.provider.net) is among the strongest spam signals there is. If you run mail, rDNS is not optional; if you wonder why a host’s “custom rDNS” support matters, this page is the answer.
How the mechanism works
IPv4 reverse zones hang off in-addr.arpa with the octets reversed: the PTR for 203.0.113.7 lives at 7.113.0.203.in-addr.arpa. IPv6 uses ip6.arpa with reversed nibbles. Regional registries delegate these zones to whoever holds the address space; the holder (your host) runs the nameservers and publishes PTRs. That is why setting rDNS is a control-panel action with your VPS provider, while forward DNS stays wherever your domain is managed. Best practice pairs them: the PTR points to a hostname (mail.example.com), and that hostname’s A/AAAA record points back to the same IP — forward-confirmed reverse DNS (FCrDNS), the loop that proves whoever controls the IP and whoever controls the name agree.
Why mail lives and dies by it
SMTP is ancient and trust-starved; rDNS is one of the few checks available before a single byte of message content. Real-world gateway behaviour in 2026: no PTR → many large providers refuse the connection outright (Gmail says so in its sender requirements); generic PTR → scored as probable botnet/consumer-line traffic; FCrDNS matching your HELO name → baseline pass that lets SPF, DKIM and reputation do the rest. rDNS does not get you into the inbox — IP reputation and authentication do the heavy lifting — but its absence keeps you out before the contest starts. Our mail VPS checklist accordingly puts PTR setup in step one.
Beyond mail: the minor benefits
Traceroutes and logs become legible (edge.yourproject.net instead of a bare address), some SSH and IRC services resolve connecting peers for display or coarse filtering, and a coherent PTR is a small professionalism signal anywhere your IP shows up. None of these are critical; mail is the load-bearing use.
Setting custom rDNS on a VPS
The flow is the same everywhere: pick the hostname (say mail.example.com), create its forward A/AAAA record pointing at your VPS IP first, then have the PTR set to the same name — here, request it from your client area and it propagates within the hour, IPv4 and IPv6 both. Verify the loop with dig -x <your-ip> +short (expect your hostname) and dig <hostname> +short (expect your IP). Two gotchas: one PTR per address is the norm (multiple PTRs confuse gateways — pick one canonical mail name), and IPv6 needs its own PTR if you send mail over it; if you cannot keep v6 rDNS straight, send mail over IPv4 only rather than over a bare v6 address.
Frequently asked questions
Can I set rDNS at my domain registrar?
No. PTR zones are delegated with the IP space, so only the address holder — your hosting provider — can publish them. Forward DNS at the registrar plus a PTR request at the host is the complete recipe.
What exactly is FCrDNS?
Forward-confirmed reverse DNS: the PTR for your IP names a host, and that host’s A/AAAA record resolves back to the same IP. The closed loop is what gateways trust, because it requires control of both the address space and the domain.
Do I need rDNS if I don’t run a mail server?
Strictly no — websites, VPNs and game servers work fine without it. It still tidies traceroutes and logs, and costs nothing, so most people set it once and forget it.
Why do generic provider PTRs hurt mail deliverability?
Because botnets send from exactly such addresses — consumer lines and unconfigured servers with auto-generated names. Gateways learned the correlation decades ago. A custom FCrDNS name moves you out of that statistical bucket.
Does VPSCrypto support custom rDNS on IPv6 too?
Yes — PTRs on your dedicated IPv4 and on addresses from your routed /64, requested from the client area with no extra charge.
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