I want to migrate a couple of Exchange 2007 mailboxes to the newly installed Zimbra server. The Exchange migration tool works fine, but it has one major disandvantage as I see it (or it could be that I don't fully understand the software ).

There is no problem to choose the user mailboxes, or infact, the user accounts in the domain. But we are mainly using linked mailboxes.
How can I migrate linked mailboxes in our Exchange 2007 to ZCS?