Solo Grant Consent to CiraSync from Office 365
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
Remove Application Consent from Microsoft Azure and Office 365
There will be one last confirmation before your request is completed.
Remove Azure and Office 365 permissions
For additional information, click on this Microsoft Article to learn more about Managing User Consent.