SELF group security help !

Hi we are in an active directory 2003 with exchange 2007

When users are trying to give delegates permission in outlook 2007 the
received this error

"The Delegates settings were not saved correctly. Unable to activate
send-on-behalf-of list. You do not have sufficient permission to perform
this operation on this object."


I found that if i had the "SELF" group to the user object, it then work fine

Now how do i give all my 500 users the self group to their object and how to
give it automaticly for new users that i will create

Thanks !

JAc