[otrs] Multiple email addresses for a customer

Is it possible to have multiple email addresses for a customer? Either that, or be able to specify a different ReplyTo email address. I want to be able to answer tickets from an automated system. Our ERP system generates emails, which are received by OTRS. When we respond to the ticket, the response needs to go to a human though. I tried using postmaster filter to assign the CustomerID, but that didn't work. Maybe there's a trick to enabling postmaster filtering. At the moment I'm using generic agent to move queue, and change the CustomerID. That works. But when agents answer the ticket, the reply goes to the ERP system. Is there a way to correct that, or force the system to reply to the customer? Kind Regards, Andrew Glossop