If the recipients of an invitation have the Spond app. they will receive a push notification if the event is cancelled (Unless they have turned off push notification in the app or phone settings, or declined the invitation).
Those that do not have the app, but that have replied that they will come to the event, will receive an SMS. Those that have not yet responded to the event, or declined it, will not be notified. Recipients who have previously registered their email address at www.spond.com, will receive an email.
If the person is only registered with an email account, they will only be notified if they accepted the invitation to the event, or it they have not yet replied.
How do I cancel or delete multiple single events at once?
How do I cancel or delete repeating events?