Vardhman spam blocking
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Normal blacklist process of zimbra is not working in vardhman, this is why blocking was implemented on postfix at smtp level.
Same has been done on all the three servers of vardhman.
su - zimbra
vim /opt/zimbra/postfix/conf/sender_access user@domain.com REJECT domain2.com REJECT
For Domain Level Rejection only domain name needs for be mentioned as shown above .
vim /opt/zimbra/conf/postfix_recipient_restrictions.cf
Add following as 2nd line
check_sender_access hash:/opt/zimbra/postfix/conf/sender_access
Create hash and restart postfix
postmap /opt/zimbra/postfix/conf/sender_access postfix stop postfix start
Reference:- http://wiki.zimbra.com/wiki/Rejecting_Emails_at_SMTP_Level