Sending a newsletter using mysql database

So thanks to all the great tutorials here I have a brilliant sign up form for my website which diligently loads people names and email address into a mysql database. I can see it all happening using phpMYadmin through my hosting provider.

Now i need to know why I’m doing all this! I was hoping there would be some way i could load up a “secret” php file online and use it to comunicate with my database and send newsletters directly.

I cant seem to find any but are there any good tutorials for this?

Many thanks in advance

Greg