We are currently using mailchimp and signed up for their integration partner Mandrill, I love how clarity has such a personal touch with each added question, we are bootstrapping, but does it make sense to add the email workflow into the programming from the start? We are working in a corporate git with CTO team. How does your programmer access the automated content? Can you set that up through a git hub wiki?
You could ask Vincent http://clarity.fm/vincentroy if you have anything further to discuss.. but here's the short version.
We built custom code for all our trigger emails & notifications, and use www.sendgrid.com for SMTP API. We looked at others, but I'm friends with the founder at SendGrid and like them personally.
For free, you can use Google Mail api (if you send less then 500 messages per day I believe). It's simple / and gets great deliverability.
Hope that helps.
P.S. The emails I write, hence the personal feelings .. it actually comes from me.