[otrs] Question about

Hi ! I´ve a question about a certain behavior in the otrs views. Why does the "customer" and "subject" in theview "my locked tickets" changed, when I get a respond-email to a ticket, where the sender of that email is not equal to the customer of that ticket ? Example: The customer of the ticket ist "T.muster@xx.com". I send an email to user "m.test@xxx.com". When I get the answer from "m.test@xxx.com" the name (From) in the view "my locked tickets" changed from "t.muster@xx.com" to "m.test@xxx.com". Is that normal ? What´s the reason ? Can I change that , so that always the customer ot that ticket is displayed !? Thanks, Steffi