
Keeping.com
Keeping™ is a customer support tool that integrates with Gmail/Google Apps. It allows you and your team to manage customers support more efficiently directly from your current mailbox without having to use an external helpdesk.
osTicket is a widely-used open source support ticket system. It seamlessly integrates inquiries created via email, phone and web-based forms into a simple easy-to-use multi-user web interface.
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