[exim] limiting exim process count?

We have a qmail server that is using ezmlm to manage a list of several
hundred subscribers.

When it sends a email (ezmlm does one to one emails) it generates 600+
single/individual emails.

When qmail sends to exim, exim immediately starts to deliver the mails
which results in 600+ exim processes trying to deliver.

Is there anyway to limit that?

I guess we could do queue runners, but that would put a delay on
outbound mail delivery..

Is there a way to queue emails 'from' a certain address so that exim can
try after it figure out that 200+ emails have to go to aol.. so that it
can try and deliver those in its most efficient manner..

(does that make sense ?)

Thanks in advance