Hello again egomouse
The only way that we know to do this is as follows;
Set both accounts up (new and old servers) in your client (we know this works in Outlook) as IMAP accounts.
Once all folders/emails have been listed, you will need to select all from your old account and then drop on the new account.
We have done this a few times internally and all has worked fine.
Apart from this, there is no other way to do it.
Matt