GETTING STARTED: Migrating On Premise Exchange Mailboxes to Office 365

MessageOps Office 365 Migrator supports migrations from Exchange 2000 and higher.

To begin the Mailbox Migration, choose the Import from On Premise Exchange option and click Next.


Next you must provide the following information to connect to your local Exchange environment.


If you want to use a CSV file, the format is the following:


When migrating from Exchange 2000 or 2003, the Exchange Server should be the server that the mailboxes reside on.  When migrating from Exchange 2007 or 2010 the Exchange Server should be a Client Access Server.

The Username specified must have full access to the mailboxes being migrated.  The domain is the Active Directory domain name (the UPN domain name) the account is in and the Password is the Active Directory Password.

The Set Target Address post migration will set a forwarder on the mailbox to the corresponding Office 365 mailbox when the migration completes.  When the forwarder is set, mail will only be delivered to the Office 365 mailbox.  To revert the changes you must manually clear the TargetAddress attribute on the user account in the local Active Directory. Make sure you fully understand what the TargetAddress attribute does before checking this box.

Next enter your Administrator Credentials for Office 365.  This account must have a mailbox.


The next screen allows you to add mailboxes to an import queue and specify the import options.


 The first thing you’ll want to do is select the source mailbox you want to import by clicking the Select Mailbox button and choosing the mailbox.  You then must select which Office 365 mailbox you want the source mailbox imported into by clicking the Select Mailbox button in the Destination Mailbox options area.

You then have several options to decide on.

Address Rewriting

Address rewriting will rewrite the Native Exchange email address format (for example EX: /o=First Organization/ou=first administrative group/cn=Recipients/cn=UserName’) which are only valid in the source Exchange organization to the SMTP address for the address entry if it can found within other message properties or resolved by looking at the Global Address List based on the Display Name of the recipient. Note because this is an automated processes exact address matching can never be 100% assured if GAL resolution is used and more than 1 contact has the same display name.

Thread Settings

In most cases these shouldn’t be modified, but here is what these settings control.

Max Threads – The number of simultaneous TCP connections to Exchange.  The Exchange server will throttle any more than 10 simultaneous connections.

Batch Size – The total number of message that will be sent in one batch.  The actual batch size will depend on the size of the messages in the batch.


The Destination is simply whether you want to import the mailbox data to your mailbox or archive.

Destination Root

The Destination Root controls whether a new folder is created for the source mailbox data.  When Separate Folder is selected, a top level folder will be created in the mailbox and the source mailbox data will be copied to that folder.  As an example, if the mailbox name was, and the Separate Folder is selected, the import would create a top level folder called and the mailbox data would be restored beneath that folder.

If the Root of Store option is selected, the top level folders of the source mailbox will be restored to the top level of the Office 365 mailbox or archive.  So the Inbox of the source mailbox will be placed in the Inbox of the Office 365 mailbox.

Destination Authentication Options

The Destination Authentication Options are very important piece of the application and it’s functionality depends on what version of Office 365 your account is connected to.

Office 365 – 2010 Exchange

With the Exchange 2010 version of Office 365, the Exchange Migrator primarily used Delegation to perform imports and exports into Office 365.  If the Exchange Migrator detects that it is connected to the 2010 version of Office 365, the Use EWS Impersonation will be unchecked and the Admin account specified on the previous remote PowerShell screen will automatically be granted access to the mailbox(es).

Office 365 – 2013 Exchange

With the 2013 version of Office 365, EWS Impersonation has to be used when working with Office 365 mailboxes, and is checked by default.  The first time an operation is performed, the account specified on the previous remote PowerShell screen will be granted the Application Impersonation Role within Office 365.

The Use Throttle switching should also remain checked as that will allow the application to switch between impersonation and delegation during the operation.

Error Processing

If the Ignore Single Property Errors is checked, if a property on a message is corrupt, the message will still be uploaded.

Email Status Notifications

If checked you can specify an email address to send notifications to when operations complete or fail.

Add to Import Queue

Once you have the Source Mailbox and Office 365 Mailbox Selected, you can add it to the Import Queue.

Once the mailboxes are queued for import, click the Start Import button to start the mailbox migrations.

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