Peekdata - Peekdata is a Schema-less, Rest based Data API Gateway to get Data from Multiple Data Sources
Hunter - Find all the email addresses related to a domain
Eligible - Payment Infrastructure for Healthcare. Eligible is a software suite that increases yield while decreasing cost to collect.
AnyMailFinder.com - Find anyone's email address
DigitalDataManager - DigitalDataManager enables users to collect customer data and behavioral events with an API.
Norbert - Norbert is an online tool that helps you to find anyone’s corporate email address.