To use Wordpress to send email, you need install the smtp plugin from your wordpress site first. For example install WP-Mail-SMTP
Please follow the steps below to install it
1. Login to your wordpress site -->Plugins-->Add New
2. Search for WP-Mail-SMTP
and install it
3. Active it
Now you can use it to set SMTP authentication.
1. Go to Settings
2. Click Email for the 'Advanced Email Options'
Note: username should be same as From Email