Using public DNS servers for Messaging Gateway

Products

• Messaging Gateway

Issue/Introduction

Symantec Messaging Gateway (SMG) is experiencing delivery issues with Outbound emails, and is using a public DNS server.

Examples might be 8.8.8.8 (provided by Google), 4.2.2.2 (provided by Level 3), 208.67.222.222 or .220 (provided by Cisco/OpenDNS).

Cause

Issues with public DNS servers

Free public DNS hosts are not recommended. Issues with these hosts include:

• No guarantee of availability for enterprise service
• Throttling/timeouts (see Introduction to Google Public DNS from the Google Developer site for an example)
• Inability to resolve for internal host names
• Public DNS traffic may not be encrypted or secured, and can provide information to bad actors.

Resolution

The recommended order of DNS host configuration is:

1. Internal DNS server in the same logical network.
2. Internal DNS server in a different logical network.
3. DNS server for the ISP/host of your external connection to your SMG.
4. Paid external DNS host.

For further reading, please review the Administration Guide for Messaging Gateway.

For more information about public DNS service and SLAs, please see each service's respective websites.