Preventing ugly announce list return address

When I send a message to an announce list, the return address in some mail clients appears as:

"; on behalf of; <>"

(looks this way in Outlook, but not in yahoo)

anyone know how I can change this to not show the dreamhost address and only show my list’s name and address?

more notes: The full headers contain a From address (my list’s info) and a Sender ( So it appears that Sender is the one I want to change or suppress.