As is usually the case, that basic Exchange/AD administration information is available on Microsoft's web site. This article applies to Exchange 2003 as well as earlier versions: http://support.microsoft.com/kb/281208/. Step 2 is the one you're probably missing.

--
Sue Mosher, Outlook MVP
Author of Configuring Microsoft Outlook 2003
http://www.turtleflock.com/olconfig/index.htm
and Microsoft Outlook Programming - Jumpstart for
Administrators, Power Users, and Developers
http://www.outlookcode.com/jumpstart.aspx

"Martin B." wrote in message ...
Would you have any documentation on this or full instructions on doing this
because I looked in AD and all I found in mailbox rights is grant all
permission but not Send As?

"Sue Mosher [MVP-Outlook]" wrote:

In Active Directory, you must grant Send As permission over the boss' mailbox to the secretaries that you want to be able to send in that fashion.


"Martin B." wrote in message ...
I got a question from a few secretaries who need to e-mails on behalf of
their boss but they do not want the receiver to see Sent by SecretaryName on
behalf of BossName, they want the sender to show as the BossName only. They
use to do it with GroupWise but since migration to Exchange 2003 we can't
find a way to do it. Is there a way to this with Exchange 2003 and Outlook
2003?