[exim] routing based on recipient address

Hej,

I'd like to set up a smartrouter for recipients hosted on aol.com,
because aol keeps rejecting my mails. Depending on the recipients domain
(aol.com) those mail should go through a smartrouter.
My problem is that I can't find any variable which covers this problem.
Is it possible with exim4?

Thanks a lot in advance,
Dirk