[Exim] Odd router config with ignore_target_hosts

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Got a strange issue with a router and ignore_target_hosts someone has set up.

What im trying to do is do a lookup on a domain and if the MX record comes back and the ip is in a particular range then pass on to the next router, which just sends like a normal lookup. If it doesnt match an ip address then send to a different transport which sends mail via a different gateway.
Now this has been set up currently with ignore_target_hosts : xxx.xxx.xxx.0/24 : xxx.xxx.xxx.0/19 etc

It doesnt seem to be working and is not passing onto the next router. Logs are saying routing defer host lookup failed.

How ever if ips dont appear in the list the router works fine as it should

Any help?

Thanks

Dave
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