Exchange Online Mail Migration Process

In this post, I document the process of migrating mailboxes from Exchange 2013 on-premise to Exchange Online when in the Hybrid Configuration.  This assumes that you have already performed the following steps:

  • Office 365 tenant created
  • Azure AD Sync setup
  • Exchange Hybrid Configuration Setup

There are other migration methods (cutover, staged).  However, in this post, I focus upon the Hybrid scenario with remote move using the MRS.

Review Technet Documentation on Migration

Email Migration Process

  • In O365 Admin Center, check that the user’s doesn’t have a mailbox on o365


  • Check the mailbox and contacts in O365


  • Go to the Migration tab and create a new Migration Batch (hit +) and “Migrate To Exchange Online”


  • Add the users to migrate who are mail-enabled in O365 and have mailboxes on-premises.


  • Specify the Migration Endpoint.  This needs to be setup before running the Migration Batch.


  • Specify the batchname.


  • Specify whether to automatically complete the migration.  I am going to manually specify it so that I can control when the cutover happens.


  • Migration synchronization process begins.


  • Once the synchronization process is complete and when you’re ready to move the user to Office 365, start the “Completing the Migration Batch” process.


  • When its completed, the user’s mailbox is now on Exchange Online in Office 365.


  • If you check the Exchange server on-premises, you’ll notice that the mailbox type for the user is now “Office 365”.


  • In Office 365, if you go to Recipients > Mailboxes, you’ll see the users with mailboxes.


  • In Office 365, if you go to the Recipients > Contacts, you’ll notice that the users that you migrated will no longer have MailUser objects listed there.


  • To allow the user to access their mailbox in Office 365, you’ll need to add the Exchange Online license to the user.
  • If you check in remote powershell to Office 365, you’ll notice by running get-user and get-mailbox that the user’s mailbox is now on Office 365 as we saw in the web UI.



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