The SMTP Ruby Sample Code by SMTP demonstrates API interaction to integrate email marketing campaigns into web services with requests and responses. SMTP provides relay service and transactional email as a service.
Shoutlet, enterprise social marketing platform, has added a contact form API to its plethora of social media services. The API allows developers to gather contact information (e.g. data from an online sign up form) and automatically update the Shoutlet contact database with the pertinent information.