Troubleshooting MX records for inbound delivery failures

Products

• Email Security.cloud

Issue/Introduction

Some or all expected inbound emails are missing in the Email Security.cloud portal.

Symptoms include:

• Inbound email is blocked or rejected
• Error: Unable to deliver your message to the following addresses: Reason: 554
• Missing the FQDN for the MX record to point to
• Sending domain is unable to send email through Email Security.cloud
• Mail is not received by the email domain.
• Track and Trace shows that email is being delivered, but the recipient is not receiving inbound emails on their gateway. 

Cause

This can mean that the MX records are misconfigured and that Email Security.cloud cannot receive your email.

Resolution

Check the following to ensure that your MX records are not the cause of your inbound delivery failures.

These requirements allow the Email Security.cloud service to scan your organization's email traffic, and ensure that all your email is directed to our scanning servers. Both primary and secondary records need to be configured, and they must be appropriately prioritized to ensure consistent mail flow.

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• You have two Symantec.cloud MX records in the following format:
  
  your-domain.com      MX preference = 10, mail exchanger = clusterX.XX.messagelabs.com
your-domain.com      MX preference = 20, mail exchanger = clusterXa.XX.messagelabs.com
  
  Note: The single "X" after "cluster" represents the cluster number you are provisioned on. The double "XX" represents the Region.
   
• The MX records have different preference values.
• No other MX records have a higher MX preference value.
• The MX record with the lowest preference value is not starting with clusterXa (it is only to be used as a backup route).
• You have the MX records set according to your New Customer confirmation email. Specifically, the number and region of the cluster. If you are in doubt, contact Support.

Note: Most DNS changes take up to 24 hours to propagate.