Is there any concerns if performing Blacklists and Whitelists
The simplest filtering methods for spamassasin are the blacklist and whitelist. Blacklist entries block all email from an address or domain, and whitelist entries bypass all filtering for an address or domain. To add blackist or whitelist entries to your salocal.cf.in file, simply add lines in the following format:
as per in the wiki Improving Anti-spam system - Zimbra :: Wiki
Valuable suggestions are highly required..
Thanks in Advance