Moving mailboxes between MS exchange servers in different branches / sites

In this scenario we had 5 sites which all had an Exchange 2007 server at each branch. The goal was to consolidate all the exchange servers into one Exchange 2010 server at the head office.

Below describe the process to take as well as some things to look out for.

  • Make sure all the exchange servers are on the latest service pack (Online mailbox moves are not supported on Exchange 2007 SP1 and earlier – Only from SP2 and onward).
  • Setup legacy DNS configuration for Exchange 2007 and 2010 co-existence. This will allow remote users to access both the 2007 and 2010 exchange depending on where their mailbox currently resides – For OWA and outlook anywhere.
    • It uses autodiscover to connect you to the exchange server where your mailbox resides.
    • You need to create a public and internal DNS A record (, the internal A record needs to point to you exchange 2007 server (Internal address) and the public A record needs to be directed to the exchange 2007 server for external connections – This can be done by publishing the legacy address if you use ISA or via a new public IP NAT that directs to the exchange 2007.
    • Note that outlook 2003 does not use autodiscover and the remote users settings would not be automatically changed over to the new exchange server when their mailbox has been moved over – You would need to manually change them.
    • You would need to create a new certificate for exchange and would need to include the legacy DNS address. So in total you would use the following in your cert:
      • (Depending on the address you use)
      • internal FQDN of your exchange 2010 server

The old cert for exchange 2007 would still need to be in place while you are doing the migration.

  • Exchange will automatically be able to route email between the old exchange 2007 and new 2010, so the SMTP NAT can point to either the 2007 or 2010 exchange.
  • In this scenario the client was using mimecast and mail was being delivered according to which exchange server the user mailbox was residing on. So after we moved a mailbox from a branch to head office we had to run the mimecast AD sync to update mimecast on where to send the mail for the user (If your exchange can route the mail from the branch to the HO you won’t need to do this).
    • Mimecast does an automatic AD sync every couple hours
    • Mimecast can only accept about 10 changes during one AD sync (So preferably run the AD sync before completing more than 10 mailbox moves)

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