Login into Lightworkers.org

Click MY PROFILE then the EDIT button.

Under the Setting ORGANIC GROUPS SETTINGS change it to..

Email notifications:
( ) Never send email notifications. Useful when tracking activity via RSS feed instead.
( ) Always send email notifications <--[TURN THIS OFF]
(X) Selectively send email notification based on the checkbox for each of my group's My Subscription page

Select under MYGROUPS which groups you would like to recieve emails from.