maybe you wouldn't have to filter such a large number of applicants if you provided any hint more specific than 'engineer' as to the kind of domains you're hiring in.
Seeing their reply, I suspect they don't actually get a "high volume of applications", it's probably a scare tactic to get people thinking there's many competitor-applicants, and thus induce a scarcity mentality.
I think convolvatron was really just asking you to add more detail (tech used, people involved, etc.) in your post. He couldn't care less about your inbox exploding.