Step 1: Open IIS manager
Go to Server Manager dashboard and Select the Tools option and Click Internet Information Services (IIS) Manager
Step 2: Configure SMTP Virtual Server
In IIS Manager, expand the server and right click the SMTP Virtual Server and then Select Properties.
Step 3: Configure Relay
Configure Server Access
- Click the Access tab and select the Relay option.
- Select the Add option to set which server is allowed to relay emails through the SMTP server.
Click OK
Step 4: Configure Security Options
Go to the Delivery tab and mentioned the intervals of retrying time limit to send outbound emails after a failed delivery, and different security options.
Click Outbound Security.
Choose any one of four security options that show in the pop up window for securing your SMTP server.
Step 5: Restart SMTP Server
Right-click [SMTP Virtual Server], select Stop, and then select Start.