Reverse DNS (PTR) for your server's IP address

Forward DNS turns a name into an IP address. Reverse DNS does the opposite: a PTR record turns an IP address back into a name. Receiving mail servers check it, so a server that sends email needs a PTR record that matches its host name. Replace 203.0.113.10 and mail.example.com with your values.

Before you start

• Know the IP address that needs the record: Services › My Services, open the server, Server Information (Primary IP and Assigned IPs).
• Choose a host name in a domain you control, for example mail.example.com.

Step 1: Check the current PTR record

dig -x 203.0.113.10 +short

Resolve-DnsName 203.0.113.10 -Type PTR

The answer may be a generic name or empty. If it is empty, no PTR record exists yet.

Step 2: Create the forward record first

Mail servers use forward-confirmed reverse DNS: the PTR name must resolve back to the same IP address. At your DNS host, create:

Verify: dig mail.example.com A +short returns 203.0.113.10.

Step 3: Have the PTR record set

HyperDC controls the reverse zones of its IP addresses, so the PTR record is set on our side:

• If your service page offers a reverse DNS option (in the Actions menu or the Manage card), enter the host name there.
• Otherwise Open Ticket, choose the server under Related Service and write the IP address and the host name you want, for example: "Please set the PTR record of 203.0.113.10 to mail.example.com."

Verify: after the change, both directions match:

dig -x 203.0.113.10 +short
dig mail.example.com A +short

The first command returns mail.example.com. and the second 203.0.113.10.

Step 4: Match the server's own host name

Give the server the same name, so the mail server announces it in its greeting (HELO/EHLO):

sudo hostnamectl set-hostname mail.example.com
hostnamectl

Make sure /etc/hosts maps the name to the server, for example with the line 203.0.113.10 mail.example.com mail, and set the same name in your mail server's configuration (for Postfix, myhostname).

Note that outbound port 25 is closed by default on HyperDC VPS. For services bought for a term of 3 months or longer, it is opened on request when you open a support ticket. Until then, send mail through a relay on port 587.

IPv6

Each IPv6 address that sends mail needs its own PTR record and a matching AAAA record. If you are not ready to maintain IPv6 for mail, configure the mail server to send over IPv4 only, so receivers do not see an IPv6 address without reverse DNS.

Troubleshooting

The PTR record shows the old name. Resolvers cache it until its TTL expires. Ask the authoritative reverse servers directly with dig -x 203.0.113.10 +trace.

Mail is still rejected for "reverse DNS does not match". The A record of the PTR name points elsewhere, or the mail server sends from another IP address. ip route get 1.1.1.1 shows the source address (src) the server uses for outgoing traffic.

The forward name does not resolve. The A record was created at a DNS host the domain does not use. See DNS not resolving.

Next steps

• The rest of the mail checks: email deliverability.
• Add IPv6 to your server: IPv6 setup.