Performing a Staged Exchange Migration To Office 365 (Exchange Online) – (Part 3)

If you would like to read the other parts in this article series please go to:

Introduction

In part 2 of this multi-part article series revolving around staged Exchange migrations to Office 365 or more precisely Exchange Online, we activated directory synchronization (DirSync) for our Office 365 tenant followed by installing and configuring the DirSync tool on the domain member server in our on-premise environment so that our on-premise users and groups were synchronized to Office 365. Finally, we installed the Microsoft Online Services Module for Windows PowerShell so that we can force a directory synchronization if needed.

In this part 3, we will continue where we left off in part 2. That is we will create a CSV file containing the batch of users we wish to migrate from Exchange on-premise to Exchange Online. We will then move on and go through the steps and post-steps that are required when migrating users to Exchange Online.

Preparing the CSV File

Okay now that we have Directory Synchronization in place, we are ready to create a list (CSV file) containing the first batch of users we wish to migrate to Exchange Online.

The E-Mail Migration tool within the Exchange Control Panel (ECP) expects this CSV file to be formatted in a specific way. The CSV file must use comma separation and the following attributes are supported in the header row:

  • EmailAddress which specifies the SMTP e-mail address associated with the respective on-premises mailbox. Bear mind this attribute is required.
  • Password is the password that will we want to set on the Exchange Online mailbox. Password restrictions that have been configured for the Office 365 tenant applies to the passwords included in the CSV file. Bear in mind this attribute is optional.
  • ForceChangePassword specifies whether a user must change the password the first time they sign in to their new Exchange Online mailbox. You can use “True” or “False” for the value of this parameter. Bear in mind this attribute is optional. It’s also important to note that if ADFS-based SSO has been deployed, this attribute must be set to “False”.

Lastly the CSV file must not contain more than 1000 rows.

In Figure 1 below you can see the CSV file we will use in this article series. It includes six mailbox users that we wish to migrate to Exchange Online.

CSV File with users to be migrated
Figure 1: CSV File with users to be migrated

Launching the E-Mail Migration Tool

With the CSV file prepared, we can move to the next step which is to launch the ”E-Mail Migration” tool from within the ECP. To do so, open the Office 365 Portal as a Global Administrator and then click ”Outlook” in the top of the screen (or ”Manage” right under the Exchange section in the middle pane).

You now see the mailbox of the logged on user. Click ”Options” in the top right corner and then select ”See All Options” in the drop-down menu as shown in Figure 2.

Opening the options (ECP) page in OWA
Figure 2: Opening the options (ECP) page in OWA

On the ”Options” page aka the Exchange Control Panel (ECP), click on ”Manage Your Organization” shortcut in the lower right corner as shown in ”Figure 3”.

Clicking manage your organization in ECP
Figure 3: Clicking manage your organization in ECP

Under ”Users & Groups” click the ”E-Mail Migration” tab (Figure 4).

E-Mail Migration tool within ECP
Figure 4: E-Mail Migration tool within ECP

This is where all the magic happens. Click ”New” and in the new ”E-Mail Migration” window that appears, enter the e-mail address of the administrative account you want to use to migrate mailboxes from the on-prem Exchange environment to Exchange Online.

It’s important to note that the administrative account that will be used to migrate mailboxes from Exchange on-prem to Exchange Online must have the necessary permissions to do so. More specifically you must assign full access permissions to all mailboxes that are to be migrated or set Receive As permissions on the mailbox database(s) containing the mailboxes. For steps on how to assign the necessary permissions see this link.

Entering the email address and credentials for the administrative migration account
Figure 5: Entering the email address and credentials for the administrative migration account

The E-Mail migration tool will now test whether it can access the Exchange on-prem environment using the Outlook Anywhere protocol (RPC over HTTPS).

Outlook Anywhere connection to the on-prem environment is tested
Figure 6: Outlook Anywhere connection to the on-prem environment is tested

On the next page we need to specify the CSV file containing the users that are to be migrated to Exchange Online. Do so then give the batch job a name and click “Next”.

Note:
After the migration has completed, the default global administrator for the Office 365 tenant will receive an email with a migration status report. If you wish to have another administrator receive the report as well, you can specify one as shown in Figure 7.

 Specifying who to migrate to
Figure 7: Specifying who to migrate to

The migration batch will now be created and the content of the CSV file will be validated. If there are validation errors, you will get a warning and be able to click details in order to see what content is invalid as shown in Figure 8.

The Migration batch contains errors
Figure 8: The Migration batch contains errors

In this specific case one of the users listed in the CSV file was listed with an e-mail address that didn’t exist in Exchange Online. More specifically, the email address for this user is ”[email protected]” not ”[email protected]”.

E-Mail address doesn’t exist in Exchange Online
Figure 9: E-Mail address doesn’t exist in Exchange Online

Okay with the error corrected, we have created another batch job and things looks much better (Figure 10). Click ”Close”.

Migration batch created without validation errors
Figure 10: Migration batch created without validation errors

You can now see the batch job is in a status created. In order for it to begin migrating mailbox data, we must click ”Start”.

Migration Batch job in “Created” state
Figure 11: Migration Batch job in “Created” state

The batch job will now go into a ”Queued” status (Figure 12) and after a few minutes (depending on number of users included) change to a status ”Running” (Figure 13).

Migration job queued
Figure 12: Migration job queued

Migration job running
Figure 13: Migration job running

To see per user details for the respective migration batch job, you can click “Open” in the lower right corner. On the per user details page, you can see an overview of which mailboxes are in progress and the items synced/skipped for each.

Per User Migration Details
Figure 14: Per User Migration Details

When all mailboxes have been migrated the status for the batch job will change to “Synced


Figure 15: All Mailboxes synced

This means that we now can delete the migration batch job by clicking on the delete icon.

Besides moving data from the on-prem mailboxes to the new mailbox that have been provisioned for each user in Exchange Online, the E-Mail migration tool will also configure e-mail forwarding for each on-prem mailbox. That is from now on all emails sent to the on-prem mailboxes will be forwarded to the new Exchange Online mailbox. Since the on-prem mailbox user isn’t converted to a mail user object, this is done by inserting the [email protected] .onmicrosoft.com address in the targetAddress attribute field for each user as can be seen if looking at a user object with ADSIEdit.

Forwarding address inserted in targetAddress field for an on-prem mailbox user
Figure 16: Forwarding address inserted in targetAddress field for an on-prem mailbox user

This concludes part 3 of this article series revolving around how you perform a staged Exchange migration from an Exchange on-prem environment to Exchange Online. Fear not though, part 4 will be published soon.

If you would like to read the other parts in this article series please go to:

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