How to Fix "554 No SMTP Service" and "Invalid DNS PTR Resource Record" Errors in Plesk Make it Rain Paper

Pre-requirements

• Administrator access to your Plesk server.
• Access to your domain’s DNS management (either via your hosting provider or ISP).
• Basic knowledge of DNS records and email server configurations.

Introduction

When sending emails from a Plesk server, you might encounter the following error messages:

554-example.com (hostname) ESMTP Service not available
554-No SMTP service
554 invalid DNS PTR resource record, IP=203.0.113.2
554-Bad DNS PTR resource record

These errors indicate that the server's outgoing emails are being rejected due to issues with the DNS PTR (reverse DNS) record. PTR records are essential for email deliverability, and without a proper PTR record, recipient mail servers may reject your messages.

Cause: Missing or Incorrect PTR Record

The error occurs because the Plesk server’s IP address does not have a valid PTR record or the PTR record is incorrect. PTR records are essential for verifying that an email server’s IP address matches its hostname, ensuring email authenticity, and reducing the likelihood of emails being marked as spam.

Verifying PTR Record

You can verify the existence of a PTR record using the dig command:

Linux Commands to Check PTR Record

Check A Record for the Domain

# Query the A record of example.com
dig @8.8.8.8 +short example.com
203.0.113.2

Check PTR Record for the IP Address

# Query the PTR record for the IP address
dig -x 203.0.113.2 +short

If the output is empty or resolves to a domain that doesn’t point back to the sender’s IP address, the PTR record is either missing or incorrect.

Resolution: Adding or Correcting the PTR Record

To resolve this issue, you need to ensure that the server’s IP address has a valid PTR record that resolves to the correct hostname. PTR records are typically managed by your Internet Service Provider (ISP) or hosting provider.

Solution 1: Contact Our Support Team or Your ISP or Hosting Provider

1. Contact our technical support team or your ISP or hosting provider and request that they add a PTR record for the server’s IP address.
2. Provide the following details:
   • IP Address: 203.0.113.2
   • PTR Record (Hostname): example.com
3. Wait for the PTR record to be added and for DNS propagation to complete, which can take up to 48 hours.

Solution 2: Update PTR Record for Cloud Servers

If Plesk is installed on a cloud server (e.g., AWS, Google Cloud, or DigitalOcean), the PTR record may need to be configured via the cloud provider’s interface. Refer to your cloud provider’s documentation for adding PTR records.

• How to Add PTR Record on AWS
• How to Add PTR Record on Google Cloud
• How to Add PTR Record on DigitalOcean

Verifying PTR Record After Update

After updating the PTR record, you can verify the changes using the same dig commands to ensure that the IP address resolves correctly to the domain.

Linux Command to Verify PTR Record

# Verify PTR record for the IP address
dig -x 203.0.113.2 +short

The output should display the correct hostname (e.g., example.com).

Additional Notes

• DNS Propagation: Remember that DNS changes, including PTR record updates, may take up to 48 hours to propagate globally.
• ISP Restrictions: Some ISPs may impose restrictions on PTR record changes. Ensure that your ISP allows custom PTR record settings.
• Match A and PTR Records: The PTR record for an IP address should resolve to the same domain as the A record for that domain.

Gotchas to Avoid

• Empty PTR Records: If no PTR record exists for your IP address, many recipient mail servers will reject your emails. Ensure that your server’s IP has a valid PTR record.
• Mismatch Between A and PTR Records: The A record and PTR record must be consistent. If the PTR record points to a different hostname than the one used in the A record, this can cause deliverability issues.
• DNS Propagation Delays: Be patient after requesting PTR record changes, as they can take up to 48 hours to propagate across DNS servers worldwide.

By configuring a proper PTR record for your Plesk server's IP address, you can resolve the "554 No SMTP service" and "Invalid DNS PTR resource record" errors. This will ensure that your server’s outgoing emails are accepted by recipient servers, improving email deliverability and reducing the chances of emails being flagged as spam. For more information on DNS management and mail server configurations, visit our Knowledge Base.