The Sendy Ruby SDK by Richard Lee allows to interact with the API to implement newsletters into web projects. With the kit, developers can subscribe, unsubscribe, check subscription status, and create campaign.
Ubivox, email marketing service, has released a number of its features via the Ubivox API. Ubivox allows marketers to create, track, and manage email marketing campaigns directly in a web browser. Because Ubivox is web-based, no additional software becomes necessary to create top notch campaigns. From simple email marketing to tips, to enterprise grade web based software tools, Ubivox aims to be the go to newsletter partner.
Email, which is one of the oldest services available on the internet, is a key mechanism via which you can reach out to your users. Over the last year, the number of services providing this infrastructure as a service has grown to include 6 email sending APIs. The newest, Amazon Simple Email Service, validates the market.