Mailchimp is one of the leading email marketing platforms on the web. Although I haven’t used Constant Contact, I’m definitely sold on Mailchimp because of the flexibility of their API. There is a very nice NodeJS project for mailchimp that allows for very simple integration. Let’s go through an example on using the mailchimp API
Ecwid has a very nice project on github that wraps mailchimp’s API in Java. Let’s cover two basic examples. If you understand how these two examples work, all of the other API calls you may want to leverage will be pretty straight forward.