If you only get an email for one server! Could you show the events for an other server that's receiving traps that you don't get emails for. And just to be sure did you change the auto rule clear the event also?
With the clear option you can tell if the event triggered your auto job for clean and email. I have had muliple setups of SIM and almosg never had any problem forwarding events. As you say tha's the whole point of monitoring so keep me informed with your progress...