You cannot enable Cached Exchange Mode on POP or IMAP accounts. Note: To enable Cached Exchange Mode you need to have an Exchange Server provided with Microsoft Exchange Account. Some of the emails may be stored in the OST file only and may reflect in the Exchange mailbox.
If you have multiple users working on a computer, any unauthorized user can access the local copy of mail data saved on that computer.It is quite difficult to share calendar entries in cached mode since calendar items will point to the local files rather than on the Server files.