Gyro Cloud Istanbul: setting reverse DNS (PTR)

1. What is reverse DNS and why does it matter?

Reverse DNS (PTR) maps an IP address to a name: 203.0.113.60 → mail.example.com. Receiving mail servers look at the PTR of the sending IP; if it is missing or the name's forward (A) record does not point to the same IP, mail may be rejected or marked as spam.

2. Automatic default record

On Gyro Cloud Istanbul every IP address (the primary address and additional IPv4 addresses) gets a reverse DNS record automatically:

• Default name: 203-0-113-60.ip.gyrohosting.com (the dots of the IP become dashes).
• The forward record of that name exists too (203-0-113-60.ip.gyrohosting.com → 203.0.113.60), so both directions match.
• When you delete the server, the service is cancelled or you release an additional IP, the reverse DNS record of that address is removed. A suspended server keeps its record.

Nothing to do; if you do not send e-mail, the default record is enough.

3. Using your own domain

1. First add an A record in your domain's DNS: mail.example.com → your server's IP address.
2. In the panel open your server's Management > Network & Security > Reverse DNS. Each IP address is a row; the status column shows Default or Active.
3. Click edit on the row, enter the fully qualified name (e.g. mail.example.com) and save.
4. The message "Reverse DNS (PTR) saved; it goes live within seconds." appears and the status becomes Active. If the A record does not point to this IP, the panel warns you (the record is still written).
5. To return to the default, click delete on the row; the record goes back to the …ip.gyrohosting.com name.

From the command line:

gyro server rdns list 12345
gyro server rdns set 12345 --ip 203.0.113.60 --hostname mail.example.com
gyro server rdns set 12345 --ip 203.0.113.60 --hostname ""     # back to default

With the API (PUT /cloud/servers/{id}/rdns):

curl -s -X PUT https://www.gyrohosting.com/api/v1/client/cloud/servers/12345/rdns \
  -H "Authorization: Bearer $GYRO_TOKEN" -H "Content-Type: application/json" \
  -d '{"ip":"203.0.113.60","hostname":"mail.example.com"}'

The response lists hostname, status (active) and default (true on the default name) for every address.

With Terraform:

resource "gyro_server_rdns" "mail" {
  server_id = gyro_server.web.id
  ip        = gyro_server.web.ipv4
  hostname  = "mail.example.com"
}

terraform destroy returns the record to the default name.

4. Rules and limits

• Only a fully qualified name is accepted (at least two labels, e.g. mail.example.com); single words such as localhost, IP addresses and internal names such as .local are refused.
• Names under gyrohosting.com, gyrodns.net and other Gyro domains cannot be used (the default name is assigned by the system).
• Well-known brand and institution names (banks, payment and shipping companies, large mail providers, etc.) are protected against abuse; if the domain is really yours, open a support ticket.
• At most 30 changes per server per hour.
• Reverse DNS is free.

5. Checking

dig -x 203.0.113.60 +short           # mail.example.com.
dig mail.example.com +short          # 203.0.113.60  (both directions must match)

On the mail server also set the HELO/EHLO name to the same name and add SPF, DKIM and DMARC records for your domain.

6. Frequently asked questions