ECWD Subscribe Add on sending notifications after editing an event

Hi,
we′re using the ECWD Subscribe Add on for Event Calendar WD. Sending newsletters/notifications about newly added events works fine. But the email notifications are sent also after an event is updated/edited which results in a huge amount of almost same emails. How can we turn off sending the email notifications to subscribers after an event is updated/edited and keep only notifications when an event is published for the first time?
Thanks for any suggestions!
Momonka