routing mail with exim4 to different mailservers

must do this to migrate mailboxes from exchange2k3 to exchange2010
i prefer postfix to do mta stuff but here we got exim4 …

the transport still exists (remote_smtp > 30_exim4-config_remote_smtp)

router:

special_routes:
driver = manualroute
domains = ! +local_domains
transport = remote_smtp
host_find_failed = defer
same_domain_copy_routing = yes
route_data = ${lookup{$domain}lsearch{/etc/exim4/routes}}

/etc/exim4/routes :
email@dumb.com: newmailserver.com
dumb.com: oldmailserver.com