It could be multiple reasons. 1. Ensure that there is no explicit deny on this account for you to access 2. Possible that if you had this second profile setup on your outlook and performed some sort of migration and now can't access this second mailbox. Will need to go to your registry and whack the profile under the windows messaging subsystem registry key Go to HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows Messaging Subsystem\Profiles\<username>\13dbb0c8aa05101a9bb000aa002fc45a Where username is the additional account you're trying to add. See if it was added before, if so delete this key. 3. Similar as 2, where your account has same legacydn and your profile is missing a particular registry key. Also try using a different machine or administrator account that has full rights and try to open the accounts that are having issues. Cannot add an additional mailbox to a MAPI profile in Exchange 2000 Server http://support.microsoft.com/kb/833399/en-us James Chong (MVP) MCSE | M+, S+, MCTS, Security+ msexchangetips.blogspot.com ________________________________ From: exchangelist-bounce@xxxxxxxxxxxxx [mailto:exchangelist-bounce@xxxxxxxxxxxxx] On Behalf Of syed faizan Sent: Monday, July 02, 2007 10:40 AM To: exchangelist@xxxxxxxxxxxxx Subject: [ExchangeList] Unable to expand mailboxes in exchange server 2003 Hi Could some one me please explain me why am i unable to expand most of the mailboxes in my account through outlook ,even though i've full access on every store along with full exchange administrator access on to the organisation Regards Syed Faizan