[exim] possible to skip router after temporary lookup failur…

Hello exim-users,

I use redirect router to verify recipient address via ldap on mc global
catalog server. Is it possible to skip the router if the lookup fails
due e.g. "server not responding" ? At the moment the mail is
temporary rejected.

The router looks like:
gc_rcpt_check:
  driver = redirect
  domains = +relay_domains
  allow_fail
  allow_defer
  forbid_file
  forbid_pipe
  verify_only
  data = ${lookup ldap {LDAP_AD_MAIL_RCPT}\
    {${local_part}@${domain}}{:fail: User unknown}}

Thanks,
Steffen