We're evaluating an Zimbra versus Exchange.

A potential migration will include the two system coexisting for a time. I understand from these forums this is not uncommon.

Our Zimbra server shares a local domain with our Exchange server. When I send messages from Zimbra to, they're sent properly. When I send messages from Zimbra to a user at who is hosted on Exchange, the delivery fails. I understand and expect this behavior but wonder how to overcome it.

Thanks in advance. We're on 7.0