Emailing after uploading

Hi,

I'm interested by this product, and i make a platform for clients.
I adapt it to have one folder for each client, a client can only see the inside of his folder,
and an admin can see all folders.

My question is how to send a mail after each upload ? I think it's not possible in the config.php, can we say me in which file I can add my code to send a mail ?