Move mailboxes between on-premises and Exchange Online organizations in hybrid deployments
With an Exchange-based hybrid deployment, you can choose to either move on-premises Exchange mailboxes to the Exchange Online organization or move Exchange Online mailboxes to the Exchange organization. When you move mailboxes between the on-premises and Exchange Online organizations, you use migration batches to perform the remote mailbox move request. This approach allows you to move existing mailboxes instead of creating new user mailboxes and importing user information. This approach is different than migrating user mailboxes from an on-premises Exchange organization to Exchange Online as part of a complete Exchange migration to the cloud. The mailbox moves discussed in this article are part of administrative Exchange management in a longer-term coexistence relationship between on-premises Exchange and Exchange Online organizations.
For more information about migrating mailboxes from on-premises Exchange organizations to Exchange Online organizations, see Ways to migrate multiple email accounts to Microsoft 365 or Office 365.
Important
You must have configured a hybrid deployment between your on-premises and Exchange Online organizations to complete the "mailbox moves" procedures in this topic. For more information about hybrid deployments, see Exchange Server Hybrid Deployments.
Important
Before you move Unified Messaging (UM)-enabled mailboxes to Exchange Online, you need to make sure that on-premises Skype for Business 2015, Skype for Business Online, and Exchange Online, all meet the requirements specified in Hybrid deployment prerequisites. For information on how to map your on-premises UM mailbox policies to policies in Exchange Online, see Set-UMMailboxPolicy.
What do you need to know before you begin?
Estimated time to complete: 10 minutes to configure the migration batch, but total time to complete the migration depends on the number of mailboxes included in each migration batch.
You need to be assigned permissions before you can perform this procedure (or procedures). For information on what permissions you need, see the "Mailbox Move and Migration Permissions" section in the Recipients permissions article.
Hybrid deployment is configured between your on-premises and Exchange Online organizations.
If you're running Exchange 2013, make sure the Mailbox Replication Proxy Service (MRSProxy) is enabled on your on-premises Exchange 2013 Client Access servers.
For information about keyboard shortcuts that may apply to the procedures in this article, see Keyboard shortcuts for the Exchange admin center.
The Microsoft 365 or Office 365 Exchange license must be assigned only after the migration is complete. You then have 30 days to assign the license.
Tip
Having problems? Ask for help in the Exchange forums. Visit the forums at Exchange Server, Exchange Online, or Exchange Online Protection.
Enable MRSProxy Service
If the MRSProxy service isn't already enabled for your on-premises Exchange servers, you must enable it manually. For information on how to enable the MRSProxy service manually, see Enable the MRS Proxy endpoint in Exchange Server.
Create a migration endpoint
The next step after enabling the MRSProxy Service is "creating a migration endpoint." For information on how to create migration endpoints, see Creation of migration endpoints.
Use the EAC to move mailboxes
You can use the Remote move migration option under the Select the migration type drop-down list on the Select the migration type page in the EAC portal to move mailboxes between on-premises organizations and Exchange Online organizations. For information on how to move mailboxes, see Use the EAC to move mailboxes.
Note
You can also use PowerShell to move mailboxes. For more information, see Use PowerShell to move mailboxes.
Remove completed migration batches
After the "mailbox moves" process has been completed, we recommend removing the completed migration batches to minimize the likelihood of errors if the same users are moved again. For more information, see Remove completed migration batches.