Zendesk - Zendesk is a beautiful, lightweight help-desk solution.

The Big Book of Churn - The definitive guide to customer churn reduction

Freshdesk - Freshdesk is a cloud-based customer support software that lets you support customers through traditional channels like phone and email, social channels like Facebook and Twitter, and your own branded community

INQ.Social - Engage with customers & apply the data to marketing

HelpScout - Help Scout is a simple, straightforward way to provide excellent support

Postmark - Postmark is the easiest and most reliable way to be sure your important transactional emails get to the inbox. Simply & reliably parse recieved email to JSON for your webapp.