Try out these steps to set up the same…..
Open ur Zimbra Collaboration Suite with userID and pass
Goto Preferences > Mail, now goto the bottom to the “Junk Mail Options” section and type / add full addresses that u wan to allow / block. (in ur case choose Allow)
Remember, most probably it allows up to 100 addresses.
Please see here for <a href=”http://www.kddi.de/English/q_a/setting/zmail.html”>Screen shot and more info</a>