What is an email API? An email API (application programming interface) gives applications access to the functionality available in an email platform, such as generating and sending transactional emails, manipulating templates, and enabling access to email metrics. Zixflow provides a service named Email API. An email API service allows you to send email communications to large lists of multiple recipients by incorporating email into your applications. Our email API allows you to send emails to users around the globe through simple RESTful APIs. You can send one email to many people, or a unique email to each person on your list with an email API service. You can send marketing messages, newsletters, updates, coupons, and invitations through email API.