Can I use UWP Mail app from a C# WinForms app?

I've been trying to invoke a UWP mail app

from my WinForms (desktop) app using this example.

I understand that I'm doing it from a desktop app, but there seems to be ways to allow it in the latest versions of Windows 10: here and here.

My goal is to be able to start a Windows 10 built in Mail app and have it open up a new email message with my subject line, message and attachment already pre-filled. (Kinda like what MAPI used to be able to do.)

But so far, if I do this from my WinForms C# app:

    private void sendEmailAsync()
    {
        var emailMessage = new Windows.ApplicationModel.Email.EmailMessage();

        emailMessage.Body = "This is a message body";
        emailMessage.To.Add(new EmailRecipient("someone@gmail.com"));
        emailMessage.Subject = "My subject";

        StorageFile file = await StorageFile.GetFileFromPathAsync(@"path-to\attachment-file.txt");
        emailMessage.Attachments.Add(new EmailAttachment(@"attachment.txt", file));

        WaitForAsync(Windows.ApplicationModel.Email.EmailManager.ShowComposeNewEmailAsync(emailMessage));
    }


    void WaitForAsync(IAsyncAction A)
    {
        while(A.Status == AsyncStatus.Started)
        {   
            Application.DoEvents();
            System.Threading.Thread.Sleep(1);
        }

    }

The call to ShowComposeNewEmailAsync throws the exception: "HRESULT: 0x80070032 The request is not supported."

So how can I make it work?