I use Mandrill for my lesson tracking app. We send out notification emails each time a new lesson is created for one of our users.
It’s working very well for us so far. The email template editing isn’t the best I’ve seen but the ability to copy/paste HTML from your own email designs is great. They offer quick previews and full (paid for) testing to see how it will render in various email clients.
You would make a call to the Mandrill API with your API key, telling to send a certain template with included values. You reference the values like:
<p>Hi *|parent_name|*. There's a new lesson available for *|student_name|*.</p>
All very simple to set up and since the email templates are all stored and edited on Mandrill you can give your clients access.
The biggest plus is that you can try out several iterations of email layouts without redeploying your app.