former user

[aw]

One of our former user was playing in many Internet-casinos. All these
casinos
send plenty of e-mails on the guy address up to now. This is bounced
back and they bounce it too. I would rather let the first message to us
die in /dev/null.
Need advice how to do it. Should I make a .qmail-user file?
How to deal with such problems If I have more of such former users?
Thanks
Andrzej