Every once in a while you need to set up user accounts with the ability to send on behalf of another user. Recently Microsoft has made this much easier to complet. Conversely, it is not in the spot we remember. Below are the NEW instructions on how to configure "send as" with Exchange 2003 SP2
1. In Active Directory Users and Computers, click the Users container or the organizational unit where the user is located.
2. Right-click the user account, and then click Properties.
3. Click Exchange General, and then click Delivery Options.
4. Click Add to specify a user..
5. Add the user you you want to be able to send on behalf of.
6. Hit OK
Now just open Outlook and pull down the from field and add who you are sending as.