When syncing calendar events between Outlook and NetSuite using ExtendSync, attendees may still receive email notifications — even if the “Notify attendees” option is disabled in your event settings.
Why It Happens
Currently, the Microsoft API does not provide a supported method to fully suppress email notifications when calendar events are created, updated, or synced through third-party integrations like ExtendSync.
As a result, attendees may continue to receive update or invite emails when events are modified in Outlook or synced to NetSuite.
What You Need to Know
The notifications are sent by Microsoft 365, not by ExtendSync.
The setting “Notify attendees” in Outlook only applies when events are updated manually through the Outlook interface — not when changes occur through API calls.
ExtendSync uses the Microsoft Graph API, which does not yet include a way to disable these attendee notifications.
Microsoft’s Status
Microsoft is aware of this limitation.
Multiple feature requests have been submitted by developers to the Microsoft Graph team.
As of now, Microsoft has not released an update or workaround to control this behavior.