Additional task-related features and issues within Microsoft Teams for business
Dear Nena,
Good day!!
I understand your concern and to my knowledge, I am sorry to convey that there is no direct feature in the Microsoft Planner to send the Outlook reminders to the users for unfinished tasks in the Plan.
I agree with you on having the ability to send the email notifications to the assigned users for unfinished tasks in the Plan of Microsoft Planner will benefit the users and I suggest you add your valuable vote in the Planner Feedback community: Planner · Community which is the best place to share our ideas and improve the Microsoft products.
However, you can achieve your requirement with the help of the custom Power Automate flow (Power Automate is a Microsoft Product). So, I request you cross-post your concern in the related community i.e., Power Automate - Power Platform Community to get the detailed help from the Power Automate experts.
Note: Please accept our sincere apologies for redirecting you to Power Automate community as the members in the category have limited knowledge on Power Automate flow, so to get the better assistance, we have redirected you in the correct path
Appreciate your patience and understanding. Have a great day!!
Best Regards,
Sophia