you to grant full mailbox access:
for mailboxes on Exchange 2003:
http://www.petri.co.il/grant_full_mailbox_rights_on_exchange_2000_2003.htmfor mailboxes on 2007:
http://technet.microsoft.com/en-us/library/aa996343(EXCHG.80).aspxand then open them from OWA or outlook by admin account