[exim] pass to next router on defer

This is a piece of my routers configuration:

provider:
        driver = manualroute
        transport = remote_smtp
        domains = ! +local_domains
        route_list = * smtp.provider.com byname

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

Is it possible to achive the following: if router "provider"
defers for some reasons (temporary smtp error from provider,
no connection with provider's smtp, etc), message should be
passed to next router "dnslookup".

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