Currently Being ModeratedFeb 14, 2013 12:25 PM (in response to Calzadilla)
Go to mail preferences>composing, and make sure under addressing: when sending to a group show all member addresses is not clicked. This is in mail 4.6 in cae you're using an older version.
Currently Being ModeratedFeb 14, 2013 2:17 PM (in response to Calzadilla)
Use BCC if you do not want addresses displayed. Email routers don't know anything about your group, and won't be able to deliver messages if the actual addresses are not included.