exim default config question

[Cream]

After the "Exim as default MTA." discussion on the fedora-devel list, i 
set out to test out Exim for the first time, based on what i currently 
use Qmail for.

(thanks to Jeff for posting his minifc3 iso, it makes it alot easier to 
experiement with fresh installations in VMware)

I'd like to use it relaying to an exchange server, with the 
relay_to_domains = example.org

but i've come to wonder about the default configuration

Under the ACL's there is a
# Accept if the address is in a domain for which we are relaying, but again,
# only if the recipient can be verified.

accept	domains 	= +relay_to_domains
	endpass
	verify		= recipient

Whats going on here? how is it verifying recipients on another server?

btw. for the Exim discussion on the devel list, the exim.conf file seems 
very straight forward and easy to understand for someone that havent 
seen it before.