Technical guide on setting up Reverse DNS (PTR records) in SolusVM 2. Learn why PTR records are critical for mail server reputation and how to map your IP to your hostname.

Configuring Reverse DNS (PTR Records) for Mail Server Reputation

A Pointer Record (PTR), or Reverse DNS (rDNS), is the opposite of an A-record. While an A-record maps a domain name to an IP address, a PTR record maps an IP address back to a domain name (hostname). For anyone running a mail server (Postfix, Exim, etc.) on a Hovixa VPS, configuring a valid PTR record is not optional—it is a primary requirement for passing SPAM filters at major providers like Gmail, Outlook, and Yahoo.

1. Why PTR Records Matter for Email

When your VPS sends an email, the receiving mail server performs a "Forward-Confirmed Reverse DNS" (FCrDNS) check:

1. It checks the IP the mail is coming from.
2. It asks the DNS: "What hostname belongs to this IP?" (PTR check).
3. It then asks: "Does that hostname point back to this IP?" (A-record check).

If the PTR record is missing or points to a generic provider hostname (e.g., node1.hovixa.com), the receiving server will likely reject the email or flag it as 550 High Probability of Spam.

2. Pre-Requisites for PTR Configuration

Before you set the PTR record in the Hovixa portal, you must ensure you have an A-Record already created at your DNS provider (Cloudflare, Namecheap, etc.) that points your hostname to your VPS IP.

Example: If your VPS IP is 192.0.2.10 and you want your mail server to be mail.example.com, you must first create an A-record for mail.example.com pointing to 192.0.2.10.

3. Setting the PTR Record in SolusVM 2

1. Log in to vm.hovixa.com.
2. Select your Virtual Machine and navigate to the Networking tab.
3. Locate the table of IP addresses. Under the Reverse DNS column, you will see your current PTR record (or a default value).
4. Click the Edit icon (pencil) next to the IP address.
5. Enter your fully qualified domain name (e.g., mail.example.com).
6. Click Save.

4. Verifying the Configuration

DNS propagation for PTR records can take up to 24 hours, but usually updates within 1-2 hours. You can verify the change from your local terminal or the VPS itself using the dig command:

# Syntax: dig -x [Your_VPS_IP] +short
dig -x 192.0.2.10 +short
    

The output should return your configured hostname: mail.example.com.

5. Technical Implementation Details

• One PTR per IP: While you can have multiple A-records pointing to one IP, an IP address should ideally have only one PTR record. If you host multiple mail domains, use the primary hostname of the mail server.
• IPv6 PTR: Hovixa also allows you to set PTR records for your IPv6 addresses. If you send mail over IPv6, this is equally critical.
• HELO/EHLO Match: Your mail server software (e.g., Postfix) must be configured to identify itself using the same hostname as your PTR record. If your PTR is mail.example.com but your server says localhost, the mail will still be flagged.

Sysadmin Advice: Use a tool like Mail-Tester.com after setting your PTR record. It will verify your rDNS, SPF, DKIM, and DMARC settings in one comprehensive report to ensure your deliverability is optimized.