Email filter for osTicket

I need a new filter action to switch the email address between sender / receiver in osTicket before register the ticket. Background: I'm sending via an external system outgoing e-mail to my customers. A copy of that email (an offer) is going into my e-mail account. That email account is imported into osTicket. The sender address is my own address, the receiver address is the customers email. OsTicket is now assigning the ticket to my own address. With a switch action in the filter I could assign the customers email address as a ticket owner. Need also help to install it on my osTicket-site.