Server Mail Error: Unable to connect to the remote server
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Server Mail Error: Unable to connect to the remote server


Article ID: 286758


Updated On:


Carbon Black App Control (formerly Cb Protection)


  • Emails are not being sent to the specified Alert Subscriber.
  • The Alert Subscriber is an "external" domain.
  • System Configuration > Mail > Test Address returns an error message similar to:
    Test mail error: Unable to connect to the remote server


  • App Control Server: All Supported Versions


This can potentially be caused by:

  • A problem with the network connectivity between the App Control server and the e-mail server
  • Third party antivirus interfering with the Reporter service
  • SMTP emails being caught as spam


  1. Verify the email configuration in Server Settings section is accurate.
  2. Log in to the application server as the Carbon Black Service Account.
  3. User PowerShell to issue the following command:
    TNC -ComputerName -Port 12345 -InformationLevel "Detailed"
  4. Verify the Server Exclusions in any antivirus/security products on the application server.
  5. Verify no SMTP email security software is blocking the email.

If issues persists, capture the Server Logs for Email Not Sending and open a case with Support.