Hello, I have an issue with some users who used to send to "all users" group. The problem started after upgrading to outlook 2010 All of the users have the permission of "send as".But they still getting the error "You don't have permission to send to" whenever they trying to send to all users group on behalf of another main mail address. please note that the main mail address have the permission to send to the "all users" group. Any suggestions how to sort out this issue. Thank you

Tried via OWA and by creating a new Outlook profile? tested in online mode too?Sukh