IMAP is best for that however I don't believe Optus support it. Probably just setting up a POP account on your phone and making sure that you have it set to retain mail on the server would be the best way to do it.
Hmm I think the S8 came with the mobile Microsoft Office platform however I don't know if it included the calendar. I know you can sync the Android calendar however I don't how you would sync the Outlook calendar with it as that is a different platform.
With the case of Android the calendar will sync seamlessly with any other Android devices. No doubt the Outlook calendar would do the same with other Microsoft devices however you are a talking cross platform and I don't think any thought was ever put into making that work.