Tony, thanks for your quick reply - you sent me on a hunt! Everything on the desktop said Outlook.Application was still correct. So I put a 30 day copy of WB on my laptop - also a Win10 machine exactly the same as the PC, except the registry switch for disabling UAC was active. It worked flawlessly. Went back to my desktop, changed the registry entry and shut off, restarted the PC. Calling Outlook.Application worked and my app was able to open a session. It's a good workaround, but I can't think it's the "correct" way?