strung,
Thank you for your continued assistance but I've found the answer that I was looking for on another site. In case anyone is interested here's what you have to do:
1. Grant the user "Send As" permission on the group in the AD via AD Users & Computers.
2. Wait for a bit of time for this information to replicate across your AD.
3. On the user's Mac, open Entourage
4. Go to Tools, Accounts, and select the Exchange server account
5. In the account properties, go to the Delegate tab
6. Under "Users I am a Delegate for", click the Add button
7. Enter the user/group name that you want to send email as to find them in the AD
8. Once the proper user/group is selected, click OK
9. Click OK to close the account properties dialog box
10. Close the Accounts dialog box
To test your ability to send as the group:
1. In Entourage, open a new email message
2. There should be a "From:" drop down box; choose the account associated with the group
3. Send a message.
If you see a message like the one in the attached file, wait a bit.
Thanks,
Alex