One of the benefits of computers (I'm old enough to remember when they came along) was that they'd make that kind of communication faster. When I was working I often got 75-100 emails a week. They came directly to me, and there was no way to delegate the responses. I made a real effort to answer every one the same day, if only with a "Thank you for writing" or "I've received your note and will get the information as soon as I can." It takes 30 seconds, and it pays off: I've been retired for five years, and I still run into people who thank me for my responses.
As a result of that, I guess, I have no patience with non-responders. He can run his business any way he wants, but if Grant Petersen at Rivendell (for instance) can answer his emails, which he does, it's hard to see why this guy can't. There are lots of good wheelbuilders out there.