A simple Drupal 7 module that integrates with Engaging Networks API which returns a supporters Opt-in preferences using their email address.
To use this you'll need to get your development environments IP's white listed with Engaging Networks against the account you wish to use it with.
Auth token needs entering in the config page.
/admin/config/services/engaging_networks_api
See the json output /ens/supporter/json/_EMAIL_