When syncing calendar events, attendees may still receive email notifications even if the Notify attendees option is disabled.
This occurs due to a Microsoft API limitation. At this time, the Microsoft Graph API does not provide a supported way to prevent these notifications when events are created or updated through the API.
Microsoft is aware of this limitation, and multiple requests have been raised by the developer community for this functionality. However, Microsoft has not yet provided support or a workaround to control this behavior.