Email Service Provider (ESP)
Also known as: ESP, Email Platform, Marketing Automation Platform
The software used to send marketing and transactional email campaigns. Think Campaign Monitor, Mailchimp, Salesforce Marketing Cloud, etc. They handle a lot of the deliverability considerations so you don’t have to. Most have advanced features like email builders, analytics, segmentation tools, and automation builders built in.
Not to be confused with an Email Client, which is the consumer-facing tool used to open emails.