SupportYard - Simple and efficient email support. Convert email requests into tickets and keep them organized
Front App - multi-channel inbox service for collaborative teams
Dynamic Campaigns by Sigstr - Share the most relevant content in every email
Drift - A messaging app that helps you grow your business.
Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.
ZenDesk - Zendesk is a beautiful, lightweight help-desk solution.