verify recipient - temp error instead of perm error

Hi,

in an acl_smtp_rcpt I’d like to deny if recipient’s domain doesn’t exist:

   deny  message = Recipient address unknown
         !verify  = recipient

I’ve a setup with some manualroute routers only, like

smarthost:
   driver = manualroute
   domains = !+local_domains
   route_list = * smarthost.domain bydns
   transport = smtp
   verify = false

To be able to check recipient’s domain  I configured this dnslookup router 
(there’s no other dnslookup router):

checkonly:
     driver = dnslookup
     domains = !+local_domains
     verify_only = true

This works so far. But if recipient’s domain doesn’t exist, exim gives a 
temp error:
451 Temporary local problem

How can I achieve that exim gives a '550 Unrouteable address'?
Any ideas?

Thanks,
Frank

-- 
Frank Richter, Chemnitz University of Technology, Germany


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