Ask HN: mailing list management service with API?

I'm looking for a service for a project I'm working on that will allow us to create mailing lists, manage addresses etc via an API, since we don't want the hassle of running our own mailing service. Ideally it would let us set the domain(s) that the list emails will be sent to. The idea would be that our customers can set up their own mailing lists via our app, and we would pass the actual work to the provider via the API. I've looked at mailchimp and a couple of others, but they seem more targeted at marketing mail pushes, rather than handling (possibly hundreds of) very small lists created by our users.

Any suggestions appreciated!