Click on the Mailbox menu on the left pane of the window to mail and communicate between admin and users.
Click on compose button marked in red as shown in the below screenshot.
Enter the following to compose a mail as shown below
*Select from the dropdown as a single user (You can also select all users)
*Single User- Enter the name of a single user
*Subject-Enter the subject text here
*Mail Content- Enter the body of the mail here
Click on the Send Message button to send the mail to the user and the message “ Mail Sent Successfully” gets popped up.