HESK is help desk software. Easy customizable it is quite extensive. Customer and administrator interfaces are easy-to-use.

Customer Interface key features:
-    Attach files
-    Submit new tickets
-    Spam prevention
-    Detailed information from customers can be obtained with custom fields
-    Related knowledgebase articles are suggested before final ticket submission
-    Staff replies can be viewed and rated.
-    Staff replies notifications can be emailed.
-    Browse knowledgebase
-    Search knowledgebase

Knowledgebase key features:
-    Knowledgebase articles are unlimited
-    Categories and sub-categories are unlimited
-    Search capabilities are easy and quick
-    Post attachments to articles
-    Most popular and newest articles can be listed
-    Rate articles.

Administrator interface key features:
-    Staff accounts and administrators are unlimited
-    Restricted access to some functionalities for certain staff
-    Ticket search
-    Tickets can be assigned to staff
-    Manage articles and knowledgebase categories
-    Modify your signatures and profiles
-    Tickets can be closed after fixed days
-    Run reports
-    Email notifications of new replies and tickets
-    Staff replies can be easily rated by customers
-    Translation feature

Summary:
HESK is help desk software. Easy customizable it is quite extensive. Customer and administrator interfaces are easy-to-use.