[Mailman-Users] I can't get "Welcom" msg.

I have installed Mailman in my RedHat6.2 OS.I sent a subscription to the maillist with a testing email account. Then I receive a msg like "Listname-- confirmation of subscription -- request 770815". I reply the msg according to it's confirmation rules. But I can't get a response msg like "Welcome to the ListName mailing list!" What 's the matter?Anyone can help me? Jack