Welcome the Technical Support section. Help us in assisting you by providing us with a concise and descriptive elaboration of your issues. Be specific and if possible, provide us with a step-by-step instruction in replicating your problem.
New group stream triggers email though notification is turned off
every group have they own notification settings. please edit the group, and you can see notification settings.
and every users have they own notification settings too, goto profile > preferences > Emails and Notifications