If mailbox-enabled users do not permanently delete a deleted
item, it will be stored on the server for a certain number of days
before it is permanently deleted by Exchange. You can set the
length of the deleted item retention period by either using the
mailbox store defaults or selecting the number of days a deleted
item is kept before it is permanently deleted.
To specify the number of days that deleted items are stored
before they are permanently deleted:
On the Start menu, point to
Programs, point to Administrative Tools, and then
click Active Directory Users and Computers.
In the console tree, expand the Windows 2000 domain.
Double-click Users, or double-click the node that contains
the recipient information you want to modify.
In the details pane, double-click the recipient you are
modifying.
On the Exchange General tab, click Storage
Limits.
In the Storage Limits dialog box, under Deleted item
retention, click to clear the Use mailbox store defaults
check box, and then in Keep deleted items for (days), type a
value.
To prevent deleted items from being permanently deleted before
they are backed up, select the Do not permanently delete items
until the store has been backed up check box.