First, you must have the correct permissions to send as the address you intend to use. If you need this setup or are unsure, please contact firstname.lastname@example.org
Restart Outlook. This will force a full Send/Receive.
Compose a New Email.
Select the "Options" tab.
Click on "From".
This will add the "From" field as an option.
Click on From, and select "Other E-mail Address..."
This will open a new window.
The address book will open.
Make sure the "tbh.com Address List" is selected.
Find the Group or Email you want to Send As.
Select it, and click OK.
The address book will close, and you will notice the From... field filled in.
The email address should now be listed in the From: field in the new email.
The next time you want to send as this address, It will show as an option in the From drop down.