We're all subconsciously trained to tune-out solicitations and spam. Think of the last time you checked your email inbox -- $50 off this, 30% off that. We get it and we're still not interested.
Your clients are the same. Impersonal, automated messages are bad. Clients simply don't like getting them, plus they'll tune out these messages. Worst case scenario? They open these emails, hit the junk button, and never see an email or awesome offer from that company again. Ouch.
You don't want to be one of those companies. No one does.