First paragraph: "When emails overwhelmed me"

IMO this is the problem with the standard App Store business model: free with In-App Purchase. In that situation, the vast majority of people who email you are not customers but rather freeloaders.

My own App Store apps are all upfront paid, which eliminates the freeloaders, so support emails never overwhelm me. Perhaps I'm not maximizing my potential revenue, but I'm doing fine and prefer this business model and relationship with users.

Even with regard to bug reports, paid customers are more invested in doing some "work", responding to my requests for more information about the issue, because they've already invested money into the app and want a return for their investment.