[exim] impose a delay on purpose?

I am trying to test things out on a working server..

how would I impose a delay on a specific recipient domain?

in my acl_check_rcpt I have:

accept
delay = 10s
domains = domain.com

what am I missing?

exim -bhc 1.2.3.4 -d+all -C /path/to/this/configure

doesn't even show that portion being evaulated..