You do not say your e-mail application but no matter...
My e-mail is BT Yahoo Mail
I am shown several system folders
Inbox - Sent - Archive - Trash - Spam.
I have no control over these.
Below them are the folders that I created and named...
If I Right Click on any of these folders I am offered...
Rename Folder
Move Folder
Delete Folder
Create Sub Folder.
Give it a try..., November 2016