[exim] adding a delay to smarthost transport

My ISP limits me to 150 emails/hr (even through their cpanel mailman
application!)
i would like to add a delay =30 secs to my own exim config so i can deal
with the mailing list 'in house'
Im using ubuntu server + exim.

Its not clear (to me) where and how to configure the delay ACL
Anyone able to offer any pointers


thanks