I need it for my internal IT ... we use ITOP but we all hate it.
It is important that people can create tickets via mail and answer tickets via mail and using LDAP Auth ...
I have 2 different support teams that cannot see each other's tickets. Both teams have different support email addresses.
OSTicket. It's free but also has a paid version.. The free version is not crippled at all. Works great. Been using it for years to support students at a college.