Well good, that's a first step.
Anyone have a solution to the recipient authentication issue in this instance? Since Zimbra can authenticate with AD, can't Zimbra accept or deny a recipient address against AD, and then if it is accepted recognize that the account must exist (according to AD) but isn't local, and therefore redirect it to a specified mail host?
dlochart - What were the Outlook connector and mobile sync problems? If you were only using Zimbra as an email gateway, why would you even be using the Outlook connector and mobile sync? Wouldn't you just leave that to Exchange, since Zimbra is only the gateway and doesn't even store any messages?