I have always found connecting with an individual or organization personally, not just a blanket form letter, to be more effective. It builds a relationship and interest in your program and students. Perhaps you could get a few moments put on the agenda to speak at a Chamber of Commerce Meeting, and / or civic clubs (Lions Club, Rotary, Community Foundation, etc.)That tends to go much further. Maybe you and some of your students could put together a promotional video (2 minuets or so in length) that can circulate on social media and can be attached to emails. That is my $0.02.