We can blacklist any email id and domain in zimbra mail server for decreasing spam mail manually. We can also whitelist domain or email id if you do not want this to receive in junk or due to any reason you do not receive mail from outside.
Blacklist email id and domain in zimbra using SpamAssassin config file
$vim /opt/zimbra/conf/salocal.cf.in (Make entry below of file)
blacklist_from *@domain.com
blacklist_from user@domain.com
Restart below service to take effect
$ zmmtactl restart && zmamavisdctl restart
Now, send testmail from outside. your mail will be discarded .
Whitelist email id and domain in zimbra
$vim /opt/zimbra/conf/salocal.cf.in (Make entry below of file)
whitelist_from *@domain.com
whitelist_from user@domain.com
Restart below service to take effect
$ zmmtactl restart && zmamavisdctl restart