Still no excuse. Any semi-competent company that is receiving that number of applications should have some sort of application to handle them. Don't meet qualifications? Either auto-reject based on information supplied, or a human hits reject. Either way, it should be able to send out a generic "form" email to the address that applied.

Literally would take no more effort than a mouse click. No excuse to not get one other than it being a shitty company.