Unable to send from shared mailbox

Hi,

We have exchange 2007 with SP2 and Outlook 2007 with SP3. We have shared mailboxes and multiple users are using these mailboxes.

Now there is a request form user is, whenever they send an email from shared mailbox, from address should be "shared mailbox name", not user name or "Sent on behalf of xxxxxx".

Can someone tell me what permission needs to be set from Exchange server so that From field will pick up "Shared mailbox name"

Mukesh S MCITP Exchange 2007