How to Send As a Public Folder From Desktop Outlook
Public Folders work a little different from your personal Exchange account. The biggest difference is that you manually have to tell it to use a From address and you also have to include the public folder email address as one of the recipients (I typically use the CC field for this) or you will not have a copy of your reply saved in the public folder. To set up your Outlook to be able to Send As the name the public folder follow the below steps.
• Open a new email
• Click Options
• Then click Show From and you will see the From field added to your email window
• Type in the email address or display name of the public folder in the From field at any time BEFORE clicking Send.