Bulk email doesn't work very well unless your emailing people that you know are already interested.
Most people won't open an email if they don't know who it's from, or unless the subject title is something of interest to them.
When sending bulk emails, you need to send them at the right time, example -
People looking to lose weight generally do this in their spare time, like the weekend, so you would send out the emails on the weekend, if your emailing about setting up a business for example, you would sen the emails during office hours, as thats when most people will be looking in to it.
There are a lot of things to consider when sending bulk emails - and watch you don't send out a load of spam, or that will make you look bad!