So for starters you haven't told us what version of osTicket your running.Q: So, my question is: is it right to set both IMAP for fetch and SMTP for sending for the same email?A: Yes.Q: If it's not the right way, is there any possible way to do this?A: To do what?Q: Like add a reply-to header for
outgoing email so when a user response to email, it'll definitely send
to a "Read only" mailbox for easy fetching?A: Via osTicket? Not that I can think of. But you ought to be able to do something similar at your mail server level.Personally if the only reason that you are asking these questions is because you are getting bounce back messages turned into tickets... the I would recommend that you make a ticket filter to deny creation of those tickets.