Step 1: In Server Manager Dashboard, select Add Roles and Features and click Next if If all the prerequisites are met.
Step 2: Select Role-based or feature-based installation under the Installation Type and Click Next.
Step 3: Select Destination Server By default, the local server is selected.
Step 4: Select Server Role and click Next.
Step 5: Select Features -> select SMTP Server. Click Next to proceed.
Step 6: Install Missing Features
The wizard prompts you to install the Remote Server Administration Tools and Web Server roles if have not been previously installed. Check the option Include management tools and click Add Features to install.
Install Web Server Role, Click Next to install the role.
Install Role Services, the default options are preselected. Click Next.
Step 7: Confirm Installation
Ensure that the Restart the destination server automatically if required option is checked and click Install.