[Exim] reducing queue using alternate smarthosts

Do i have an alternative to speed the server for incoming e-mail and other
services than running a cron every ten minutes with "
exim -C alternateconfig -q 0xxxxxx 0yyyyy"
to pass all waiting messages to a "spare smarthost"
Also, how to avoid to pass to this other smarthosts message frozen due
" local MX pints to localhost" or that are undeliverable due local reasin
(for example an alias pinting to a temporarily in\accessible file)