sending bulk

Hello everyone :) I want to send automatic emails to potencial clients (planning to send about 200-400 emails per day). Need your advices, because it will be my first time, when I will send emails this way. I providing services and have an website (personal domain). Which email should I use for...

Okay, let's call it by its actual title: Does spamming work? If it does, then I'd like to know how to do it the right way. If it doesn't work, then why people are still doing it?