The Postmark PHP SDK by Wildbit allows API interaction with the aim to simplify email communication. References include guides for installation and API calls. A sample displays how to send a first email from the app.
Email doesn't need postage, right? Is that old hoax about the postal service charging per message finally coming true? Not really. But PostageApp may be a service worth paying for if you want to send email from your application.
ODesk claims to be the future of work, or more recently: "Work 3.0." So it should come as no surprise that the next version of work comes with an API. If you’re not familiar with the platform, oDesk provides contractors and companies with a hourly billing system which both verifies the work done for the company, and guarantees payment to the contractor.