I'm trying to setup a feedback loop with the Yahoo.com email network, but it appears that it requires a DKIM signature. This is something I've been trying to setup for some time, so its a good as an excuse as anything.
Since I use Postfix, it appears that a milter is the method to use. I've never setup a milter before, but its something I've wanted to do for awhile.
Another alternative is to use dkimproxy. For my company, that may be the better option as I find proxies to be more flexible.