Suppose you have Outlook 2000/2002/2003 users who access additional mailboxes (usually firstname.lastname@example.org, email@example.com, firstname.lastname@example.org etc.) on an Exchange 5.x/2000/2003 server (other mailbox setup in the Microsoft ExchangeService). When they reply to or forward from that mailbox the message goes into their primary (usually personal) mailbox sent items. UniSent utility lets the message to stay in the mailbox that it originated in (i.e. sent item goes to Sent Items folder of the mailbox the item was sent from).
The license based on the number of users that actively use the product. 5-licenses pack costs $200; 10-licenses pack costs $350; unlimited pack costs $1500.