To do this the ticket opener would have to populate a custom field that you setup with the information.You could then use the custom field in the email template in the subject. Custom variables, such as those you add via Admin panel -> Manage -> Forms can be accessed using the name that you gave them and the prefix of the built in form that you added them to. So if you added a field called Agency that was added to the built in "Ticket Details" you would access it as ticket.agency, aka:%{ticket.VARIABLE}where VARIABLE is the case sensitive variable name you gave the form field. Data associated with "Contact Information" is available via %{ticket.user.VARIABLE}.