Outlook Issue connecting to mailbox

We have a user who is relocating to a different office (London) from our HQ in Boston.  The London office is a child domain of the Boston office, all within the same forest.  In Boston, we have Exchange 2010 running, but in London we are still on Exchange 2007.  I disabled the user's mailbox from Exchange 2010 in Boston, then created a new user account in London.  Then I re-connected the disconnected mailbox to the new account in London.  Now, when attempting to connect Outlook to the mailbox that lives in Boston, I get the following message "Cannot open your default e-mail folders.  Microsoft Exchange is not available.  Either there are network problems or the Exchange server is down for maintenance."  Any thoughts on how to resolve this?
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AmitIT ArchitectCommented:
Why you disabled it. You can move mailbox to London server. Or create new ID and mailbox and merge old mailbox data.

Also run clean-mailboxdatabase command on 2010 server and check again.

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