(thanks
We have set-up another domain, which is not filtered via MailFoundry, and it goes straight through. So yes, there's something not-quite-right between MailFoundry and Zimbra. But MF have been doing this for a number of years, and while that in itself doesn't mean they can't screw up, it handles "relaying" to a number of other servers (including other postfix, qmail, exchange

, and more..); it sounds a bit too simple, gut feeling.