Webmail, as well as other office products, will sometimes default to the light version on a mac. to get the full version, follow these steps:
Make sure you are on the latest Chrome which right now happens to be 59.0.3071.115
Next, make sure you are on the latest MacOS. As you know, Google is very big on security and doesn't allow certain features on OS (Windows included) that it deems a risk. This should be macOS Sierra 10.12.4 or higher
Next, make sure you are going to http://o365.letu.edu and logging in from there with your letu.edu account. Once logged in you should get the main menu of all the apps
Click on Mail and you should see Outlook loading. If you get the light version, follow these steps to enable the standard version:
Sign out of the light version, close Chrome and restart the process above.
There are additional suggestions in this article: https://support.office.com/en-us/article/Outlook-on-the-web-Light-2aec8c2d-da48-4707-ba37-c800e1c284cd