• If the hostname cannot be resolved from the Commander application server, confirm DNS records.
• Run these commands:

  nslookup [Host Name of SMTP Server]  
  ping -a [IP Address of SMTP Server]

• Check that the hostname and IP address match in both outputs. If mismatched, DNS entries may be incorrect.
• To bypass DNS, either update the Windows hosts file or use the SMTP server’s IP address directly in the configuration.
  
  

SMTP port availability

• By default, SMTP uses TCP port 25, but your mail server might use a different port.
• Use a port scanning tool (for example, Port Scanner) to confirm the port is open between the Commander application server and the SMTP server.
• Ensure the configured port matches the SMTP service port.

Relay permissions

• SMTP servers frequently enforce allowlists or denylists to control email relay.
• If you lack administrative access, confirm with the mail server administrator that relay is permitted for the Commander application server.
• For detailed references, see:
  • SMTP Relay Config for Microsoft Exchange
  • Sendmail Relay Controls
  • Postfix Relay Access

Additional troubleshooting

• If tests succeed but users do not receive emails:
  • Ask recipients to check mail filtering and junk folders.
• If issues persist:
  • Enable debug logging for SMTP by following the Controlling Commander Logging Level instructions.
  • Re-run the test.
  • Submit diagnostics using Submitting Snow Commander Diagnostics.
  • Turn off debug logging after collecting the diagnostics.

Outcome

Applying these steps helps isolate DNS, port, or relay-related misconfigurations and verify whether Commander can successfully connect and relay messages through the SMTP server.