[exim] Outgoing IP address

Hi,

I have an exim4 server running which sends out email to various places.
Whenever it delivers to aol.com email addresses mails are rejected, as
the IP address it is sending from doesn't have reverse DNS setup.

I'd like to have exim4 send email from the main IP address of the server
which has reverse DNS, is there a way to achieve that?

TIA,

Morten