Mailman — strange behaviors

Hello folks, I already made mailing with mailman and 10.3.9 Server. Today I made an new list with 10.4.3 Server. My mail server work perfectly since more than 9 months. So I've created my list using Server Admin, adding two friends on this list (there email addresses are correct). When I send a messsage to my list, they never received it. I found no error on postfix log. I've checked the mailman archives and my messages are in this archives. In fact it seems like mailman work internally but don't want to deliver message to recipients. I've checked and repairs the permissions (check_perm -f). I don't know where to look now. Any help will be appreciate. Thanks in advance, Jacques