[exim] manualroute and queueing

I have a smart router set up to funnel all outgoing mail from exim
through my ISP's mail server:

smart_route:
driver = manualroute
domains = !+local_domains
transport = remote_smtp
route_list = * smtp.sbcglobal.net

The only thing I dislike about this is that it takes a long time for
the process to complete, which requires the client to sit and wait for
the whole process. Can someone suggest a way to have exim queue mail
for the smart router, and issue a bounce if some problem occurs? As it
is, it takes a minute or two for a client to send a mail, which isn't
really pleasant on the user's end.

Thanks for any suggestions.

--
Mark Edwards
mark@???
cell: +46704070332