You can prevent mailbox-enabled users from receiving e-mail from
specific users by specifying that the mailbox-enabled user can
receive e-mail from everyone except recipients you specify.
To specify who the mailbox-enabled user cannot receive e-mail
from:
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 mailbox-enabled user you
are modifying.
On the Exchange General tab, click Delivery
Restrictions.
In the Delivery Restrictions dialog box, under
Message restrictions, select From everyone except,
and then click Add.
In the Select Recipient dialog box, under Name,
select the recipients that you do not want the mailbox-enabled user
to receive e-mail from, and then click Add. Repeat this step
for each recipient.