The site that I got my information from was: Audio Device Class Inactivity Timer Implementation (Windows Driver Kit)
My "IdlePowerState" was set to 04, which is D3Cold in their terms; I changed it to 03 (which I assume is D3Warm, and which I also assume is the pre-Windows 7 setting); it made no difference. Since this is a desktop and not a laptop, I ignored the ConservationIdleTime setting (since that applies to running on battery power), and I increased toe PerformanceIdleTime from 012c (or in the registry, "2c 01 00 00") which is 300 seconds, to "2c 0f 00 00" which is about 67 minutes. and so far that seems to have fixed it. I assume if I'm idle for over 67 minutes and then I get an email, it'll "pop" again, so my choices are to change the IdlePowerState to 00, or increase the PerformanceIdleTime to an even bigger value.