If you don’t want to use an add-in in Outlook 2013 or Outlook 2016 for Windows, you can disable it so it won’t show up in your messages. In Outlook, click File > Manage Add-ins. Tip: This opens Outlook on the web. Under Manage add-ins, in the Turned on column, uncheck the box for the add-in you want to turn off. Tip: To turn the add-in back on, check the same box.