[exim] dnslookup router pass to other router if error

Hi all!
Since I work with exim 4.xx I have a lot of problem to send email using
Dnslookup transport.

So my question is, is there a way to configure exim to bypass dnslookup
router and go to the next if dnslookup fail???

Here are my router configurations

dnslookup:
driver = dnslookup
domains = ! +local_domains
transport = remote_smtp
ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
#no_more

smart_route:
driver = manualroute
domains = ! +local_domains
transport = remote_smtp
route_list = * relay.skynet.be


So what I want to do is to pass the mail to my smart_route router if
dnslookup fail.

Regards

Cédric MARCOUX