I am running osTicket (v1.8.5) on IIS
Maybe you should consider an upgrade to the latest version (1.9.3). It's hard to remember when which feature was added and also there are several bugs that were fixed, new features for added and existing ones improved in the meantime. I know it's sometimes hard to keep all software and services in a company up to date, but for osTicket it's definitely worth it ;) (and don't forget to backup your database and osTicket installation directory)