The CaptainForm – Google Groups integration will allow you to collect new contacts to your Google group. Go to Settings → 3rd Party Apps and look for the Google Groups logo on the apps list.
Type in the name of the group and select the field that is email validated on the form.
To make sure your submitters don’t skip filling in their email address, make sure you set your Email field on the form as required.
Go to Editor, select field and go to Edit Field → Options → Required.
Tick the Enable checkbox on the top-right corner of the box to enable or disable the integration whenever needed.
Click on Remove to completely remove the Google Groups application from your online form.