An email blaster is a service or piece of software that allows you to send an email to a large number of people. An email blaster differs from an email client because email blaster programs have relationships set up with email service providers ensuring that the people who are using their blasting program to send emails are not spam. It is important not to use your everyday email client to send out emails to large numbers of people because email service providers will look at the address, see that it is not verified (like email blasting programs are) and "black list" your address as spam, effectively saying that your email messages should automatically be routed to recipients junk mail folder or trash.

Another advantage of using email blasting programs is that they track recipients' interactions with your messages. You're able to see how many people opened the message as well as how many clicked on specific links in the message. Some examples of email blasting programs include Constant Contact, Mad Mimi, Vertical Response and Mail Chimp.