Outlook Web Applet
Webmail is a way to access your e-mail with your own web browser without installing any special programs (or apps) or using a special device.
Outlook Web Applet is a web based e-mail client. It checks your browser brand and type prior to giving you access. If you, for instance, use Google Chrome on Windows OS it will give you access to all functionality ("Premium") but if you use a browser that is not on the list of approved browsers, for instance Google Chrome on Chrome OS, it will give you access to only a part of the functionality ("Light").
Many people object to browser detection even for detecting whether the browser is capable of showing the page. This is not the reason that I object to OWA. As the example above shows, its list of approved browsers has nothing to do with capability of the browser. The Google Chrome browser for Chrome OS has the precise same capabilities as Google Chrome for Windows OS.
By installing Microsoft Web App, ISC encourages (and for some functionality forces) you to use a web browser approved by its own software supplier. This is even true if you read your e-mail from home. Such an arrangement is very valuable for Microsoft and undoubtedly the university has bargained a very lucrative contract with Microsoft in exchange for giving it the power to boycott its competitors from inside university systems.
I however think that limiting access for students and staff of this university to their own e-mail and files is a very aggressive marketing strategy. It violates the idea of open access (Dutch). With its decision to use OWA as its only web based e-mail service (Dutch) the Radboud University board goes against its own strategic plan where it claims to promote academic independence and information accessibility.