[quadrifoliate]

> sometimes they are genuinely busy and they literally cannot spend countless hours to respond to every candidate they've spoken to tell them "No, we've passed on you".

We work in the software industry (well, a lot of us do). If individual human effort is not scaling, we write programs. "Dozens" or "hundreds" of candidates should be a cinch for a simple script to keep track of what candidates have been passed on; and they can be informed with a simple form letter.

If you don't have anyone at your company capable of writing these kinds of tools, maybe you should focus on hiring that person first. It will pay off in the longer run.