The support module provides a basic ticketing system and helpdesk that is native to Drupal, offering complete email integration.
The Support module offers the following features:
Ticketing activity is illustrated with colorful charts (depends on the Chart API module). Tickets can be assigned to users (and users can view all tickets assigned to them). Tickets support states (new, active, pending, closed, etc) and priorities (low, normal, high, critical, etc). Configurable email notifications for new and updated tickets. Email integration allows tickets to be created and updated via email, with support for attachments. New users can be automatically created. Ticket properties can be updated via email (using included support_mailcmd module). Highly configurable client and user ticket overviews, highlighting tickets that haven't been updated for a long time. Fully integrated with Drupal's search functionality, users can only search for tickets they have access to. Supports an unlimited number of clients, each with their own configuration and access permissions. Tickets are nodes, ticket updates are comments.