[CentOS] need trouble ticket system

Hi,

I need to implement trouble tracking system,
we have 250 users in one premise & 3 desktop support technicians.

I need to implement trouble ticket system, where user will enter their
application / other issues. Mail will be sent to technician available on
duty.
trouble ticket will be provided to user & will be given close stat once
resolved.

Kindly suggest me one such application based on open source.
-- 



Regards
Dhaval Thakar
http://dhavalthakar.blogspot.com/