OpenSupports!

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. Manage, organize and archive all your support requests and responses in one place while providing your customers with accountability and responsiveness they deserve.

Freshdesk is an award-winning, online help desk software that allows you to support customers over email, phone, the web or even through Twitter and your company's Facebook page. With Freshdesk there is nothing to download or install, you don't have to worry about server upgrades/patches and your agents can support customers from anywhere. Popular features include:

OTRS is the leading help desk software solution that makes the communication with your clients more transparent and easier. From incidents to service requests, with the web-based Open Source help desk software, OTRS, no communication is lost and customer requests are routed automatically to the right service team, ensuring they are answered more quickly. Free of license costs and with an open and flexible architecture OTRS makes it possible for service organizations to build a customized and powerful service management solution resulting in high-quality service at minimal operational cost. Since Version 5 OTRS offers responsive design and works on any mobile device. A new chat feature including webRTC based audio and video chat, appointment calendar for improved team collaboration and resource planning plus fully encrypted messaging is now available. »

Help Scout scales like any other help desk, but the customer experience is personalized like a normal email.

RT is an enterprise-grade ticketing system which enables a group of people to intelligently and efficiently manage tasks, issues, and requests submitted by a community of users.

Brimir is an open source helpdesk system. It allows you to send and receive support emails through a friendly web interface.Received emails are converted to tickets, which can be assigned to agents.

Price: FREE, Language: PHP/MySQL, Type: Web-based, Features: unlimited tickets, categories, knowledgebase, attachments and more.

Kayako is effortless customer service software that helps teams be more productive and build customer loyalty.

Jitbit HelpDesk is helpdesk software that has same price for ANY number of technicians. And it has everything a help-desk needs: 2-way email integration, asset tracking, knowledge base, file attachments and more.

Zammad is a web based open source helpdesk/customer support system with manyfeatures to manage customer communication via several channels like telephone,facebook, twitter, chat and e-mails. Do you receive many e-mails and want to answer themwith a team of agents?

Helpy is written in Ruby on Rails 4.2 and released under the MIT license. Features include support tickets with email integration, community discussions, multilingual knowledge base and more:

With an innovative user interface, studied to offer a completly streamlined experience, Deskero takes care of the clients in the most simple and straight forward way, through both the traditional channels (mail and web) and the newest social media.

The Vivantio Platform is a comprehensive IT service management solution chosen by enterprises for its flexibility, reliability and configuration and integration capabilities.

Zent.IO is a Contact Center Cloud Software Multichannel that unify chat, phone and e-mail. All the communication channels will be answered from a single interface. The agent will only need a web browser