Hi, we've started deploying Zimbra servers in environments where they replace the existing mail server. It's been refreshing to have the beautiful web interface and also the increase in its ability to deal appropriately with spam over the solutions it has replaced. However, we also have some clients who aren't ready yet to part with their Exchange servers. In this case I'm wondering if at least as a first step, some of the improvements in spam detection and tracking could be had by putting the Zimbra server in front of the Exchange server as sort of a mail relay. With the postfix restriction that addresses must exist on the server in order to be accepted - that alone could cut down on the number of SMTP connections we're having to deal with. However, ideally, Zimbra would authenticate addresses on the domain without having to actually set the accounts up manually on Zimbra, and then it would pass the messages on to the Exchange server rather than storing them locally. Is this feasible?