Active Directory accounts that have mailboxes must be created in Microsoft Exchange Server 2007 prior to migration.

Use the New-Mailbox cmdlet to create users who have Exchange 2007 mailboxes based on the users that you specify in the comma-separated value (CSV) file. For information about how to use the New-Mailbox cmdlet, see New-Mailbox (RTM).

For information about how to create the CSV file, see How to Create a CSV Text List.