I've updated my port of Courier-MTA to version 0.39.3. Testing and feedback are welcomed. Note: I corrected a problem with files in both /var/courier and /var/run/courier. As a result, you'll want to flush your mail queues before upgrading, or risk losing emails. Download the port: http://www.shockley.net/OpenBSD/courier-0.39.3.tgz