Hello, we are currently using Zimbra as a secondary mail server, for testing and making a smooth migration, moving one user at a time from Exchange to Zimbra. Our online antispam service will expire soon though (we are using blackspider), and we don't want to renew it as it is quite expensive - so we would like to use Zimbra's antispam feature.

So we want to put Zimbra as primary, and our Exchange server as secondary; that way Zimbra could filter the spam before it get delivered to exchange.

So here is my question: does Zimbra filters spam on mails to mailboxes it is supposed to forward to?