There are many different services that provide this kind of functionality.
For example:
http://sendgrid.com/ (One of my favorites)
http://www.streamsend.com/
http://mailchimp.com/
They're all going to charge you for their services though. In return you'll get high deliverability as well as all kinds of analytics. Send Grid has a great set of API's.
There are probably tens if not hundreds of other companies that offer the same kinds of features out there.