go to user cp on tool bar just below TRT Logo, then select edit options, scroll down to messages, there is a box to select whether you want email notification to replies, make sure its checked 
HMMM,,,,,,,,,,,,,,,,,,,,,,,thefatman said:odd.. been happening to me latley too. i've only been getting emails for one thread, instead of all the threads i posted too. not a big deal, since i half live here anywayjust something i noticed.