An email service provider (ESP) allows users to send email campaigns to a list of subscribers. Email service providers are technology companies that make it easier for people to build email lists and send emails. As email marketing has become a more popular marketing channel, more email service providers have sprung up to provide differentiated services. At the most basic level, an ESP needs to do two things: store email addresses and send emails.

An Email Service Provider, commonly referred to as an ESP, is the technology a business employs to manage and deliver email marketing communications. These solutions are generally hosted on servers and also operate the necessary hardware and/or software to deliver bulk emails

An Email Service Provider or ESP is software used to run email marketing campaigns at scale. It can also refer to email clients like Gmail and Outlook. The main purpose behind using an ESP is to send mass emails to a list of subscribers in an organised way. Yet, most email service providers today offer many extra features that make the process smoother.