If you no longer want your contact to be notified when you open their return envelope, you can change this setting directly in Outlook.
Open Outlook .
Click on the Secure Exchanges tab.
Access your Settings .
Select the Envelope Options tab.
Uncheck the option:
"Notify the recipient when I open their return envelope."
Click on "Save settings" to save your changes.
If you do not click Save , the change will not be applied.