I modified /etc/sysconfig/dkim-milt changed CANON=simple to CANON=relaxed/relaxed and this seem to do the trick. Problem solved!
I have setup dkim with postfix using this tutorial http://www.howtoforge.com/set-up-dkim-on-postfix-with-dkim-milter-centos-5.2 and it seems to be...
Separate names with a comma.
