Billing tickets on the reaction time, the implementation and other
LDAP — authorization and import users.
Full access control system based on groups.
Interactive web interface.
No limits to tockets and users.
Can fetch tickets from IMAP/POP3/NNTP.
Long time update system by one click.
iOS-app and PUSH-notifications.
Russian, ukraine и english interface language.
By all actions with tickets and users.
Try communication, as in social network system.
Pushbullet.com and other sms-api.
Can connect system to other services and systems.
Can configurate mail templates via Code.
You can use web-interface on all devices equally comfortable.