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Network

Reverse DNS

Setting the PTR record for your addresses, and why mail servers refuse a machine without one.

Reverse DNS answers "which name belongs to this address". It is a PTR record on the address, and it is set on our side because the address belongs to our network, not to your domain.

Why it matters ​

  • Mail. Receiving servers check that your sending IP has a PTR, and that the name it returns resolves back to the same address. Without it, your mail is rejected or scored as spam before it is read.
  • Logs and tickets. A named machine is readable in traceroutes, access logs and support threads.
  • TLS and monitoring tools frequently display the reverse name, so a wrong one is a lasting source of confusion.

Set it ​

  1. Create the forward record first: an A record (and AAAA for IPv6) pointing your chosen name at the address, in your own DNS zone.
  2. Then set the PTR from the IP management on the service page in the client area, or by ticket if the option is not available for your service.

Order matters. A PTR that points at a name with no matching A record fails forward-confirmed checks, which is what mail servers actually test.

Good to know

One name per address, and the same name in both directions. mail.example.com in the PTR, an A record on mail.example.com pointing back to the same IP, and the same name in your SMTP HELO.

Verify it ​

bash
dig -x 203.0.113.10 +short          # PTR: mail.example.com.
dig +short mail.example.com         # A:   203.0.113.10
dig -x 2001:db8:abcd::10 +short     # IPv6 PTR

Both answers must line up. If the PTR is right and the A record is missing, the check still fails.

Propagation is a matter of minutes, but resolvers cache the previous answer for as long as its TTL. A negative answer that is still cached is the usual reason a correct PTR looks broken for an hour.

Sending mail from a dedicated server ​

A PTR is necessary, not sufficient. Providers also want SPF, DKIM and DMARC on the sending domain, and they weigh the history of the address. A freshly assigned IP has no reputation, so ramp your volume up rather than starting at full rate.

Reviewed on September 1, 2026