You need to test whether or not SMTP authentication is working with Symantec Messaging Gateway.
telnet <SMG_IP_address> 587EHLO mailserver.comAUTH LOGIN334 VXNlcm5hbWU6dXNlcm5hbWUuY29t334 UGFzc3dvcmQ6bXlwYXNzd29yZ$4Note: If you receive an error from this point forward, double-check the password and encoding.
If you need to manually convert the username and password, search online for a base64 encode and decode tool.