For me, I didn't need the HTTP Passthrough plugin or any extra settings for this to work. Users were able to log in with their AD credentials and if it was their first time, a user account in osTicket was created automatically for them.
Today i tried again and now works! And When the AD user don't have email, the Create account screen appears with the information of user, asking to add the email. My osticket version is 1.9.4Thanks!