Removing User Consent from Office 365 For CiraSyc; CiraSync uses the Office 365 APIs to get access to user mailboxes so that it can create and update office 365 global address list, contacts and calendar appointments. When you signed up for CiraSync, you granted consent to https://dashboard.cirasync.com :
Removing user consent so that CiraSync can no longer access your mailbox, you can visit this Microsoft link: https://myapps.microsoft.com to see all applications that have access to your Office 365 / Azure account.
Click on the ellipsis (1) and select Remove (2) from the menu
There will be one last confirmation before your request is completed.
For additional information, click on this Microsoft Article to learn more about Managing User Consent.