Assigning Multiple Mailboxes in Exchange 2000

Microsoft Exchange Server 5.5 lets me assign more than one mailbox to a single domain account. Exchange 2000 Server doesn't seem to offer this feature. Am I missing something?

Exchange 2000 and Active Directory (AD) permit only a one-to-one (1:1) mailbox—AD user account relationship. However, you can work around this restriction and give one or more AD user accounts full access to more than one mailbox. To do so, open the Microsoft Management Console (MMC) Active Directory Users and Computers snap-in. Open the Properties dialog box of the AD user account whose mailbox you want to share with other user accounts, then go to the Exchange Advanced tab. Add the other user accounts to which you want to grant mailbox access, then select the Read Permissions and Full Mailbox Access check boxes (under the Permissions section). Next, go to the Properties dialog box's Security tab and allow the accounts you just added Send as and Receive as permissions.