The Outlook Home Page allows you to customise the default view for any folder in Outlook. This allows specifying a URL to be loaded and displayed whenever a folder is opened. This URL has to be either HTTP or HTTPS and can be either an internal or external network location. When Outlook loads the remote URL, it will render the contents using ieframe.dll, which means we have numerous options available to us for customising the page. To do this, the Outlook ActiveX controls can be used.”]
Source: https://sensepost.com/blog/2017/outlook-home-page-another-ruler-vector/