Please have a look at
This is the Inbox folder. Incoming mails you can find at the folders cur, new and temp.
Also you can find the folders
and self created folders with the same structure.
The admin user is not the same as the root user, but you can set the admin mail address to the root user.
At the server manager move your cursor to the root user at the upper right corner and click on profile. Here you can set the admin mail-address to get root mails at the admin account.