By watching this video user can easily unsubscribe a Plan from emails in Microsoft Planner.
Steps for this feature are as follows:
1) Access Microsoft Planner through Office 365 portal. User can view all plans in 'Planner Hub'.
2) Select the plan and go for 'More options'. Select 'Edit plan ' from drop down list. 'Edit plan' window will open.
3) To stop notification simply uncheck the box at bottom. Click on 'save’ to save the changes. Click on task card. click on the option as 'Assign to'.
4) Search for name to whom user wants to assign the task. Open Outlook client to see the notification about this activity.
5) Here user can see that there is no notification.