Facebook SDKs enable you to pass app event data from your app to Facebook. With app event data, you can accurately track and measure the actions people take in your app.
Gmail is a free, advertising-supported email service offered as part of Google's G Suite, with 15GB of storage, color-coded inbox filters and unsend button.
Zendesk is an cloud-based customer service software solution trusted by over 40,000 organizations worldwide. Companies such as Groupon, Box, and Zappos are using Zendesk to lower costs, raise productivity, and increase customer satisfaction.