The process of how to migrate mailboxes between Exchange 2007, Exchange 2010 and Exchange 2013 is identical to moving mailboxes between databases in Exchange 2013 (see Chapter 5, Configuring External Access for more details). Depending on how many users you have to move, you might want to take a different approach though.
To execute the following steps, you will need access to the Exchange Admin Center and Exchange Management Shell.
We will cover certain number of tasks in this section.
Depending of the size of your organization, you will either move users all at once or in several batches over several days, weeks, possibly even months.
The first thing you should do however, is test your Exchange 2013 environment by conducting a pilot. The pilot involves moving a small set of regular users that will be moved to Exchange 2013 ahead of the rest and validate that everything is working as it should.
Picking...