[exim] Testing if a host name exists

OK - I got the syntax right - thanks for everyone's help - but now
working on the functionality.

Here's what I need to do.

I need to determine if a host name exists. mail-in.domain.com

If the domain exists - accept the message.
If the domain doesn't exist then skip this router and go on to the next one.
If there is a DNS error - skip the router and go to the next one.

This code has a problem in that when it fails it defers. Don't want any
defers. How do I do this?


process_and_forward_auto:
driver = manualroute
require_files = /x
domains = +preprocess_auto_domains
condition = ${if match{$h_X-Spam:}{HIGH}{no}{yes}}
transport = remote_smtp
route_list = * "${lookup dnsdb{a=mail-in.$domain}{$value}{fail}}"
no_verify