EMERGENCY! Mailing to Pre-foreclosure List Question

I have my list of Pre-foreclosures and it has NOD’s and NFS’s (notice of foreclosure sale) as well. Would it be best to only mail to the NOD’s? Or should I mail to the nfs’s as well. I don’t know how I can help them if their house is already on its way to auction. I am super tight on money and I don’t have the extra cash to test whether both will work or just the nod’s. Please help. I want to send them today but its getting late and I need to know what to do.