Through outlook 2003 we can edit the users group membership. Double click the "To" from the received mail window, click on "member of".... from here we can change the group for teh users.....Is there a way we can prevent this. It can be from outlook or Exchange server. I'm using outlook 2003 connecting to Exchange 2003. Thanks & regards Yusuf md_yusuf_is@hotmail.com

You make sure that the user does not have permissions to do so! If he is DL owner he can change via Outlook and check your AD Permissions for users that can change groups Deli