[otrs] Reply to Auto reply problem

Hi, I'm looking for solution in otrs-auto response functionality, currently we have configured mailbox(pop3 enabled),any gent/customer sends a mail ,this would create ticket in otrs.auto response for this also configured,which in turn would send mail to agent/customer for ticket created.This functionality is working fine. Problem is when agent/customer replies to "Auto-reply" message of OTRS,another ticket is created.what i'm looking for is,when user/customer mails back i.e."replies to auto-reply",this should be added as notes but not another ticket should be created.