NYC Letter of intent question

I sent out my letter of intent on the 24th of June and it was received on the 25th of June. I sent it certified mail so the tracker said it was received. I haven’t received a response back yet. Does anyone know how long it takes to receive the packet? Or if they are sometimes late? Maybe I’m just being too paranoid they didn’t get it. If someone has any info on this that would be great. Thank you!