How to disable qmail bounces?

[Cygon]

Hi!

Occasionally my postmaster account receives a failure notice, telling me that an email could not be delivered and that the bounce message bounced again. This is a known problem, allright.

I found numerous guides on the net that tell you how to send those double bounce messages to /dev/null. Which is crap. Your server still happily bounces messages. A spammer needs to do nothing more than to put the recipient's email into the From: field, send it to invalidaddress@yourserver.com and your server will happily distribute spam all into the world. That's just as good as an open relay.

Can I somehow either force qmail to check whether the email address in the To: field actually exists at SMTP time and reject the message while it is uploaded?
Alternatively, I'd settle for a catchall account at /dev/null but the SMTP time rejection would be cooler because the original sender, whoever he's posing to be, would have to deal with the failures.

Thanks ahead,
-Markus-

[nobspangle]

bounce messages are generated by the sending server if a smtp server connects to yours and sends