CString is a c++ class that is rather specific to the MFC framework (and to ATL, for the nitpicks). Therefore, you cannot send a CString outside of MFC (not even to vanilla C++). Well, technically you can send it, but the recipient will not be able to make any sense out of it.
However, CString does have an AllocSysString()
] member function that will allocate an automation compatible BSTR type string. The API copies the contents of your CString object into this BSTR and returns it.