We think we've fixed the email issue we were having. Many thanks to the support folks who worked long hours to make it all happen.
Here's what we've done:
People in the "All Email Users" group can select the categories they want to get email for... and whether they want emails for new discussions, replies, or both. But they will not get email until they "opt in" -- You do this by logging in, editing your profile, and changing your Notification Preferences.
As a convenience, we have gone ahead and "opted-in" a few dozen of the most frequent users. We have set ALL these folks up to get email from the NTDEV and from Administration and Announcements categories only -- So, if they want to NOT get email for NTDEV, or they DO want to get email for NTFSD or WINDBG, they need to login, edit their profile, and change their Notification Preferences.