How can I get osTicket to generate a reply when a ticket is resolved (or closed)?

Your question is not clear can you explain a little bit more? Do you want osticket to send an email when you close/resolve ticket? regarding ticket status?

This is not a feature in osTicket. If you want to do something like this then you would want to create a canned response and select it at the time you close the ticket.

Write a Reply...