If the mail aliases are the same, then you should be able to use DiRT to back it up
- Then if you do not have SQL on the box, you could try uninstalling the mail configuration, which will disassociate it from Ex5.5, then rerun configuration setup to reassociate with the new 2000.
- If you have SQL on box then it probably easier to reinstall Unity to a clean system in the new environment, then use DiRT to restore. Upon restore it will plow through Exchange and try to match up all of the subscribers to mailboxes. If all of the mailboxes have already been migrated and the aliases remained the same then you are in good shape. If not, then it gets more difficult.
Let us know.
Steve