I have a customer with many subdomains and several gateways. One of the gateways is for outgoing purposes only. But I want to redirect recipients with customers subdomains to to the internal interface on their main gateway instead of sending theese mails to the MX record destination due to problems with BigIP and FW (I cannot do anything about that). Any other mails are to be sent according to MX record of their domain. I just cannot figure out how to to this.