qmail-relayreject is a simple tweak for qmail which allows the rejection of all mail coming from a host that appears to be an open relay; the test is not particularly subtle, but it *is* fast. Hosts identified as open relays are palmed off to a modified qmail-smtpd called qmail-relayreject which sends 553 sorry, no mail accepted from an open relay; check your server configs (#5.7.1) in reply to any MAIL, RCPT or DATA command. It uses a small program called 'relaytest' to check remote hosts; this is used via a small shell script shim placed in your /service/smtpd/run (see INSTALL for details) Please send all mail to qmail@; qmail-relayreject's website is http://www.trout.me.uk/qmail-relayreject/ NB: qmail-relayreject was done in an afternoon because I wondered if I could. It has had some testing, but it would still be a *very* bad idea to set this up on a live system without trying it on a test rig first (try port 26, maybe). Then again, this is probably true of any change to your mail system.