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Drift - A messaging app that helps you grow your business.
Zendesk - Zendesk is a beautiful, lightweight help-desk solution.
Zendesk for Startups - Everything you need for seamless customer conversations.
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
Live Chat by Sumo.com - Instantly communicate with customers, prospects & visitors