Both Gmail and free Microsoft accounts (outlook.com, hotmail, msn, live, and other free domains provided by MS) allow calendar sharing from their web interfaces, but do not allow the sharing settings to be configured from third-party apps such as eM Client.

So to share these folders, you need to access the web interface and share the calendar there - but eM Client will be able to synchronize any calendars shared with you, so you can still view all the shared calendars from inside the program!