How to grant Send As for Exchange 2003?

Grant “Send as” permissions
If you grant a user “Send as” permissions for another user’s mailbox, the DelegateUser can send mail as the MailboxOwner. The From box in these messages appears as follows:
From: MailboxOwner
To grant a user “Send as” permissions for another user’s mailbox:

1. On an Exchange computer, click Start, point to Programs, point to Microsoft Exchange, and then click Active Directory Users and Computers.
2. On the View menu, click to select Advanced Features.
3. Expand Users, right-click the MailboxOwner object where you want to grant the permission, and then click Properties.
4. Click the Security tab, and then click Advanced.
5. In the Access Control Settings for MailboxOwner dialog box, click Add.
6. In the Select User, Computer, or Group dialog box, click the user account or the group that you want to grant “Send as” permissions to, and then click OK.
7. In the Permission Entry for MailboxOwner dialog box, click User objects in the Apply onto list.
8. In the Permissions list, locate Send As, and then click to select the Allow check box.
9. Click OK three times to close the dialog boxes.