The procedure below assumes the following setup:

Client > Internal MTA > IMSS > External MTA (10.0.0.1:25)> Internet
Account used user@domain.com to authenticate
IMSS's default relay is set to 10.0.0.1 - this sets imss to send all other mails intended for domains not listed in the domain based delivery to 10.0.0.1

To use SMTP authentication:

1. Back up the tsmtpd.ini file.
2. Open the tsmtpd.ini file and go to the [SmtpClient] section, and then add the following parameters:
    

   The modification is made on the DefaultRelay. This means that all mails will be forwarded to the declared MTA if the recipient domain does not have any smarthost configured.

   [DefaultRelay]
   SmartHostCount=1
   SmartHost0=10.0.0.1:25:1: user@domain.com:<encrypted password>
   UseMethod=1
   DNSServerCount=0

3. As stated in the tsmtpd.ini file, you must encrypt the password. Open a command prompt, go to the IMSS bin folder, and execute password.exe.

   Syntax:
   <imss\bin folder>\password.exe <password>

   A set of characters, which is the encrypted password, will be generated.

4. Enter the encrypted password in the password area of the "SmartHost0" parameter.
    

   The [DefaultRelay] must be added. This is commented by default.
5. Save and close the tsmtpd.ini file.
6. Restart the IMSS SMTP service.