If you are receiving duplicate notifications across different devices, it is likely because iPhones and Androids typically end up creating two notifications for an open event. When a mobile device opens the email, two data requests are made - one from the IP of the phone and one from the IP of a data center.
Since there are two unique requests with different IPs and "locations," we send you two notifications.
If you have further questions or concerns about this, please reach out to Yesware Support.