With the send icon in the top corner, you can send the case with all it's history and attachment except private logg, by e-mail.
 
In the "User" field you can enter the user / customer's last name, first name, username or phone number. The field searches as you type.
Under the user info icon, you can look up more information and edit information  
 
 

 
If the user is not registered in AD, you can add user to the More Service base by pressing the + character in the user field: 
Mandatory fields (Name, Username, User group) are marked in red.