The Exchange Migrator uses both EWS and MAPI to connect to mailboxes to Import and Export data, so it is critical that both these protocols are enabled on the Mailboxes you use with the application. By default these protocols will be enabled on any mailbox you create through the Administrative Console with the exception of Kiosk Mailboxes.
Note on Kiosk Mailboxes
A Mailbox that has a Kiosk licence isn’t accessible using Outlook/Mapi so Importing or exporting from these Mailboxes is not possible.
For Mailboxes where MAPI has been disabled by an Administrator to prevent access, this will need to enabled for the application to work. MAPI access can be either Enabled or Disable though the Exchange Administrative console eg.
These setting can also be configured Remote Powershell and the Get-CASMailbox and Set-CASMailbox
Eg. To get the current settings
To Enabled MAPI on a Mailbox you can use
Set-CASMailbox –Identity mailbox -MAPIEnabled:$true -EwsEnabled:$true