OTRS

OTRS is an Open source Ticket Request System (also well known as trouble ticket system) with many features to manage customer telephone calls and e-mails. The system is built to allow your support, sales, pre-sales, billing, internal IT, helpdesk, etc. department to react quickly to inbound inquiries.
It is distributed under the GNU Affero General Public License (AGPL) and tested on Linux, Solaris, AIX, FreeBSD, OpenBSD, Mac OS 10.x and Windows.

You can use OTRS for your own product and customize for your requiarements. OTRS is developed using Perl.

Feature List

Web-Interface:
Agent web interface for viewing and working on all customer requests
Admin web interface for changing system things
Customer web interface for viewing and sending infos to the agents
Webinterface with themes support
Webinterface with Single sign on (e. g. HTTPBasicAuth or LogonTickets)
Multi language support (Brazilian Portuguese, Bulgarian, Czech, Chinese, Dutch, Danish, English, Estonian, Finnish, French, German, Greek, Hungarian, Italian, Norwegian, Polish, Portuguese, Russian, Slovak, Spanish, Turkish and Vietnam)
customize the output templates (dtl) release independently
Webinterface with multi attachment support easy and logical to use

Email-Interface:
MIME support (attachments)
PGP support
SMIME support
dispatching of incoming email via email addess or x-header
autoresponders for customers by incoming emails (per queue)
auto convert of incoming html only emails to text/plain (to get it easier searchable)
email-notification to the agent by new tickets, follow ups or lock timeouts
follow up check based on references and in-reply-to header
Ticket:
custom queue view and queue view of all requests
Ticket locking
Ticket replies (standard responses)
Ticket autoresponders per queue
Ticket history, evolution of ticket status and actions taken on ticket
abaility to add notes (with different note types) to a ticket
Ticket zoom feature
Tickets can be bounced or forwarded to other email addresses
Ticket can be moved to a different queue (this is helpful if emails are for a specific subject)
Ticket priority
Ticket time accounting
Ticket print view (PDF)
Ticket pending feature
Ticket responsible feature
Ticket bulk feature
Ticket hook divider
Ticket event module layer
Generic agent to do automatically actions on tickets (based on scheduled jobs)
content fulltext search
Ticket ACL support
Ticket workflow feature
System:
ASP (activ service providing) support
Calendar / WorkingTime support for time calculations (SLA)
Customer Source can be used from a SQL databases or LDAP (e. g. eDirectory, AD, OpenLDAP)
TicketHook free setable like 'Call#', 'MyTicket#', 'Request#' or 'Ticket#'
Ticket number format free setable
database xml interface (driver for different databases including admin tasks like ALTER, CREATE, DROP, ... of tables)
database layer, support of different SQL databases (e. g. MySQL, PostgeSQL, Oracle, DB2 and MSSQL)
a stats framework
utf-8 support for frontend and backend
OTRS web package manager (to install applications like calendar or filemanager)
agent authentication against database, ldap, httpauth or radius
customer authentication against database, ldap, httpauth or radius
creation and configuration of user accounts, groups and roles
creation of standard responses
creation of sub queue
signature configuration per queue
salutation configuration per queue
email-notification of administrators
email-notification sent to problem reporter (by create, locked, deleted, moved and closed)
submitting update-info (via email or webinterface)
deadlines for trouble tickets
global TimeZone feature
Web config editor
Link support of objects link tickets, faqs, ...
different levels of permissions/access-rights
easy to develope you own addon's (OTRS API)
easy to write different frontends (e. g. X11, console, ...)
a fast and usefull application

Personal View
OTRS is a very complex system and architecture.