The add-in installation may fail when installing the Visual Studio Tools for Office (VSTO), which is required to run the Microsoft Outlook snapADDY add-in. Normally, VSTO is installed if necessary during add-in installation; however, sometimes installing VSTO manually may help.

If you already have VSTO installed, or are not sure, you will want to remove the existing installation first. Follow these instructions:

  1. Save all open work and completely close Microsoft Outlook if you have it open.
  2. Open the "Add or Remove Programs" dialog in the Windows Control Panel. For this type e.g. "Remove" into the windows search and choose "Add or Remove Programs"
  3. In this dialog, locate the "Microsoft Visual Studio 2010 Tools for Office" item. Once clicked, an "Uninstall" link should appear in the toolbar above the listing. Click this to uninstall VSTO. If you do not see this item, VSTO is not installed and you can proceed with the installation instructions below.

Visual Studio Tools for Office setup can be downloaded directly from Microsoft. Click the 'Download' button on this page to download the vstor_redist.exe file to your computer. Once this file is downloaded, run the installer.