HelpScout provides an email-based customer support platform, knowledge base tool, and an embeddable search/contact widget for customer service professionals.helpscout.com
The Gainsight Customer Cloud brings together the technology you need to ensure your customers are happy. They aggregate data from many different sources, helping make customer management easier.
Zendesk offers a customer service and sales CRM software designed to create better customer relationships. Their support ticketing system can help you track and prioritize customer support interactions.
Front helps teams collaborate in one inbox. Just @mention teammates to share and work off of the same email, get their input with internal comments on the message, and draft a replies together without sending edits back and forth.