[exim] dk-filter for DomainKeys with Exim4

Hi -- I have exim4 correctly signing with DKIM signatures but I would also
like to add a DomainKey signature. I am running Exim 4.72 on Ubuntu 10.10.
I understand that DomainKeys support doesn't come with the pre-combiled
binary; I would prefer to not re-compile my mail server. I installed
"dk-filter" which runs as a daemon on port 4445. I'd like to figure out how
I can get outgoing emails to pipe through the local daemon for signing on
their way out. Any help or suggested configuration is greatly appreciated.
Thanks.