block mail to a particular domain

[Johnh]

I have just upgrade from 5.0.2 to 5.0.10. I am sure this was not happening before the upgrade but I may be wrong. the problem is spam related.

My server is behind a FW and so all connections to it appear to come from inside my network. I have spam/antivirus on but I am not sure than the spam part is working. It is running but I if I grep the zimbra log for "SPAM" it is empty - I used to have lots of them before!

I have postgey installed and this is working.

I've adjusted the /opt/zimbra/conf/amavisd.conf.in file and this also works.

What I need now is to be able to block ALL main being SENT to a particular domains: the TO address is being forged so the mail appears to be coming from my domain but is being relayed to a small range of yahoo addresses (yahoo.com.tw mainly). Is there a way to block any mail be sent there?

Thanks.