Hi Mathan,
If you want stop email notifications for the users, then you have to disable it from each accounts.
When you do it from account settings, it means that you have disabled from your account. If you want to do it for all the users, you can write a insert query (though it is not supported).
<sql:update>
insert into clb_notification_prefs values (getdate(),${UserID},getdate(),${UserID},${UserID},'NOTIFICATION_TIMESHEETS_TYPE','EMAIL')
</sql:update>
Please let me know if you need any additional details.
Regards,
Teena Antony