Junk mail relay in split domain scenario

[PNE]

I think that someone already had to solve this before. Zimbra as secondary in split domain scenario, so it routes all incoming messages for non-local mailboxes to the MS Exchange smarthost. So far so good. But Zimbra also forwards messages that are junk - these that are between Tag and Kill values and if it was local mailbox, they would end up in Junk folder.

Any chance of making Zimbra to not forward these ones?

[CMuelders]

Let them be tagged in the subject line (e.g. [SPAM]) and use an Outlook rule.

[PNE]

I would like to see a Zimbra server solution if possible.