Step 1 : Open forms from Office portal and click on Group Forms as shown below.

Step 2 : Select recent group form

Step 3 : Select any form that you want to enable the notification.

Step 4 : You may see a number of group members shown as below,Click on it and it will redirect to Outlook webmail groups

Step 5 : Click on edit and select edit group settings.

Step 6 : IMPORTANT ! Make sure the highlighted check boxes are checked and make sure save the settings

Step 7: Go back to the forms and select on the respective form and click on the ellipsis button (...) on the upper-right corner of your screen and select on Settings from the drop down.

Step 8 : IMPORTANT ! Make sure the highlighted check boxes is checked in order to receive the email whenever there is a response on the form.

That's how we enable the notification for forms to receive in outlook.