Go to User CP > Edit Options. Then scroll down to Default Thread Subscription Mode and select Do Not Subscribe.
After doing so, you will no longer automatically be subscribed/receive emails about threads you've simply posted to. BUT if you want to subscribe to a particular thread after doing that, you can always go up to the Thread Tools link at the top of a thread and select to subscribe to a thread in the little drop-down box that appears. Then you will only receive notification of the ones you really want.
Last edited by nycindie; 06-26-2011 at 09:27 PM.