ME020531 - TRB: 503 SMTP error when sending to locally hosted addresses.


Unable to send to locally hosted addresses.

Error: 503 This mail server requires authentication when attempting to send to a non-local e-mail address. Please check your mail client settings or contact your administrator to verify that the domain or address is defined for this server.


  • Inbound SMTP authentication has been enabled
  • Incorrectly set permissions are preventing file lookups.


Inbound SMTP authentication:

Navigate within the administration console to: Servers>localhost>Connectors>SMTP. Right click on "SMTP" and select "properties". Next navigate to the "Advanced SMTP" tab and use the dropdown menu within the "Inbound authentication" section and select "Do not require authentication".

Checking for permission failures:

Run the Mail Enable Diagnostic Report and check for permission failures on the MailEnable "Config" folder. If failures are present run the Mail Enable "meinstaller.exe" utility located within the Mail Enable "BIN" folder and execute the option "common installation" to reset the permission settings.

If the "meinstaller" option does not help then a file monitoring utility can be used to monitor file activity and check for permission failures. "Process monitor" can be downloaded from:

Run "Process monitor" and filter on the "MESMTPC.exe" Mail Enable service. Next open up a command prompt and perform a telnet test to the Mail Enable server. Once completed the test inspect the "Process monitor" log output for any "Access denied" errors.


How to perform a telnet test: Article ME020207


Product:MailEnable (Pro-Any Ent-Any)
Keywords:503 inbound local authentication
Class:TRB: Troubleshooting (Configuration or Environment)
Revised:Wednesday, May 4, 2016