Outlook Addin Check (VSTO)
I published new build of Outlook addin check for VSTO. I've added drag&drop so you can drag and drop your addin into the window.
If you have earlier build (below 5) you will have to uninstall the previous version before you install the new build (I messed up somewhere...).
UPDATE:
Here is MSI installer for Outlook addin check. I haven't found any solution to install the app behind the proxy server.