To send bulk emails you get two options
1: Black Hat Method
2: Services
To talk about Black hat Methods, actually you'll have to run a mailer script on any server and put all of your emails there, it will send the message in bulk to all, (Test different servers to make sure your email hits the inbox).
the Second method is to go for any paid service, MailChimp is one of the famous, cheapest and relaible mailing service i would recommend.