[otrs] How to remove "New Message"

Hi. What actions do an agent need to perform to remove the "New Message!" status on a ticket? Apart from closing the ticket. Our agents would like to remove the "New Message!" on tickets where they have already seen the message but are unable to do anything about it at the moment. -- Lars Jørgensen Netværksadministrator Gyldendal A/S Tlf. 33 75 57 95