[otrs] attachment while closing a ticket.

Hi , while closing a ticket , when i add an attachment and inform the customer by mail i want the attachment attached to the mail just like when they open a new ticket to the agent the attachment comes to my mailbox also.. i want the same while sending the attachment back to the customer. so the customer can see the attachment in the mail... customers send some small files for correction we correct them and send them back. is it possible? and how? probably it should be enabled somewhere... thanks sarper