[exim] Outgoing INterface

Hi all,

I would like the set the outgoing interface address based on the domain that is sending it.

Each domain on our servers has its own IP address.

Simply using the MX address does not work because some of our domains use a mail filtering service, so the MX does not match the sending address.

Question, how can I modify the line below to set the interface to that of the MX, if that fails, is the A record, if that fails, use the servers ip address.

remote_smtp_local:
        driver          = smtp
#       interface       = ${lookup dnsdb{a=${lookup dnsdb{mxh=$sender_address_domain}}}}
        helo_data       = $sender_address_domain
        return_path_add = true