Direct Mail is a Mac OS X app for designing email newsletters, as well as creating and sending email campaigns. Includes campaign performance monitoring, subscriber list management features, and Mac business app integration capabilities. The RESTful Direct Mail API can be used to programmatically add, update, and delete messages, mailing lists, and campaign reports. To use the API, a user must have Direct Mail version 4 or later installed. API requests are authenticated with basic HTTP and authorized with an API key.