Front - multi-channel inbox service for collaborative teams
HelpScout - Help Scout is a simple, straightforward way to provide excellent support
Hiver - Manage Customer Support, Sales and Projects right from your Gmail inbox. Collaborate with Shared Labels, Shared Contacts, email notes, email reminders and email templates
Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.
Missive - Team communication app now supporting FB, Twitter & SMS
GoSquared Live Chat - Beautiful, simple, and free live chat for your website