We done similar type of migration..
First let me know how many user mailboxes are hosted on godaddy?
If it's less let's cofigure it on outlook and convert it to pst.. then restore the respective pst file on zimbra using pst migration wizard. .
Note: Do not change or modify mx record on DNS before backup
If you change you will not able to login into godaddy mail accounts..
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Last edited by firstname.lastname@example.org; 01-24-2014 at 08:31 PM.