Hi Adele,
Sorry,Windows 10 Mail app cannot be interfaced using MAPI, nor using OLE Automation. Basically this means you cannot integrate Windows 10 Mail app into a PB application. Instead, Windows 10 has a new Email API for "UWP" applications.
What I would do? I would get a colleague to write a .NET assemly wrapping the the email functionality, have that .NET assembly registered as a COM Callable Wrapper - and that way have an interface that your PowerScript code can call using traditional OLE Automation.
Sorry, /Michael