This patch permits to qmail to reject messages coming from a sender has not a valid dns entry.
Created attachment 19844 [details] New patch (qmail-1.03-mfcheck.3.patch)
sorry, i'm going to have to reject this one, for the specific reason that it breaks authorized relaying (RELAYCLIENT lines in /etc/tcp.smtp). no patch should break existing legitimate functionality.
*** Bug 69516 has been marked as a duplicate of this bug. ***