The Postmark Node.js SDK by Wildbit allows API interaction to implement email features into applications. Installation code included. References explain how to send an email and send a batch of messages.
Startups need to build quickly and iterate quicker. That means not re-inventing the wheel -- whenever possible. Just 5 years ago, people were asking why would you use an API? This has quickly turned to why wouldn't you! Since March 2007 there are 14 times as many APIs listed on the ProgrammableWeb site. And the growth rate is accelerating. API listings on ProgrammableWeb have exploded this year so far, doubling the same period last year, and about four times the same period in 2010 (see chart below).