how can i stop receiving mail message for every post in my forum

Go to your Profile=>Preferences and look for this option "Always notify me of replies :
Sends an e-mail when someone replies to a topic you have posted in. This can be changed whenever you post." and choose No. Note that you still have to go to the "Watched topics" tab and remove all the topics from there so that you won't receive any e-mails when a member posts. To remove a topic from that list check the box next to it and then click on the"Stop watching the selected topics" button.