Does Zimbra keep emails that are sent to an address that does not exist on the server? i.e. when the domain is accurate, but the local-part isn't.
Our Exchange server had a "post office" that these kinds of emails went into.
(And yes, this is still stemming from the disaster I mentioned in my "When is a feature not a feature" post. A DJ found an alias that's been missing for a month and he wants his lost "listener feedback" back.) ><