postfix help

Hi please help me.How can i make my outgoing mails to be put on hold
queue before they are send out of mine mail server.Please help me.

i have put some header check in my main.cf file and create a file /etc/
postfix/Header_checks and in that file i have written /^Received: /
HOLD.My all mails are getting in hold mail.Now i want only outgoing
domain mails should go into hold queue and local mails should be
delevered into there mail boxes.Please help me regarding the same.