[exim] outgoing smtp rate limiting ?

Hello,

I would like to limit the rate of messages an Exim (4.50) server can
*send* by smtp, something like maximum one message per second. I do
not want to limit the incoming rate.

Is this possible ?

Thanks.

Some details of my current configuration:

1) router

smarthost:
        driver = manualroute
        domains = ! +local_domains
        transport = remote_smtp
        route_list = * <smarhost1>:<smarhost2>

2) transport

remote_smtp:
driver = smtp