Zammad is a free open source, a fully-featured web-based ticketing system for helpdesk or customer support. It ships in with a multitude of features for handling customer communication through various channels such as social networks (Facebook and Twitter), live chat, e-mails as well as telephone. It has an API for integrating your telephone system into in and outgoing calls.

Zammad Features:

Supports full-text search.

Has flexible text modules.

Immediately reports changes to objects.

Supports auto-save.

Supports individual escalation or setting client solution time limit.

It is auditable and often used in banks.

Allows for creation of individual overviews.

Supports various security mechanisms such as device-logging and two-factor-authentication.

Provides a customer interface, where they can track the current editing at any time.

Supports external authentication via Twitter, Facebook, LinkedIn or Google via OAuth.

Supports nine languages and so much more.