It' very simple changing amavis config:
put in /opt/zimbra/conf/amavis.conf*
read_hash(\%whitelist_sender, '/etc/zimbra/whitelist');
read_hash(\%blacklist_sender, '/etc/zimbra/blacklist');
read_hash(\%spam_lovers, '/etc/zimbra/spamlovers');
In /etc/zimbra/* put sender address or domain, one per line. Wildcards allowed.
Eg:
hotstuff@sexnzen.com
getassistedgroup.com
A spamlovers list is for that accounts that always need to receive all messages, even if spam. According to rfc 2822 postmaster, abuse and other account of this kind should be spam lovers.
Ciao,
Claudio