[exim] Backup-MX

Hello,



I am having a bit of a problem with configuring exim to be a backup mx
but with a setup that only forwards mails to a certain ip-range.



What I need to do is setup a mailserver that:

Accepts mails from all world

Only forwards mails that are sent to a domain that is based on my
IP-ranges

Bounce all other mails.



The thing is that I have no way of knowing which domains are on the
IP-ranges.



I am fairly new to exim, so I'm not all deep in how the config works,
but I think that it is something I should define either in the
acl_check_rcpt or remote_smtp.



My problem is that I cannot see how I get the IP for the domain the mail
is bound for. I can find the Ip for the host that is sending the mail,
but that is somewhat irrelevant, as I only need to check on if the mail
is bound for an IP in our range.



Help is greatly appreciated





Best regards

Anders