Topic: Creating new mail subfolders & where's mail stored?

Does anyone know how to create local subfolders for email messages. I'm on k-@ mail pro using my own IMAP mail server & would like to create local folders for engineering emails on my Galaxy Note Pro 12.2". Just something I've done for years on notebook computers without leaving loads of stored mail on the server. With my high volume of mail & ftpfile storage, I'm close to quota....  Thanks  John