Vyte connects to Office 365 using the Oauth 2 protocol. This protocol is great because it never gives third parties (like Vyte) that need to access your data to provide value (like Vyte does) access to your Office 365 password.
Instead Microsoft gives third parties only access to the data they need (your identity, your calendar and your contacts in the case of Vyte).
If you want to then revoke us that access you can then easily do so from your Office 365 settings. Make sure to only do that if you're sure you won't need to use Vyte in the future, as this will break your connection to Vyte.
These are the steps:
1. On office.com, click on your picture on the upper right corner of the screen and click "My account" in the menu that unrolls.
2. On the left column of the "My account" screen, click on "App permissions"
3. Find the "Vyte" card and click on the "Revoke" button.
The following screenshot sums it up: