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Mailbox Migration to Exchange Online

Exchange Online
 

Applies to: Exchange Online

Topic Last Modified: 2014-08-29

You can use the Migration dashboard in the Exchange Administration Center (EAC) to migrate mailboxes and mail content from an on-premises messaging system to Exchange Online and your Office 365 organization. You can migrate mailboxes and mailbox data from Exchange 2013, Exchange 2010, Exchange 2007, and Exchange 2003, or migrate mailbox data from an IMAP messaging system.

Contents

Remote move migrations

Staged Exchange migrations

Cutover Exchange migrations

IMAP migrations

Compare migration types

Exchange Server 2013 Deployment Assistant

Plan to coexist with a third-party messaging system using Active Directory Domain Services

A remote move migration is used to migrate on-premises Exchange mailboxes to Exchange Online in an Exchange hybrid deployment. You must have an Exchange hybrid deployment to use a remote move migration. With a hybrid deployment, you get the following capabilities:

  • User account management in your on-premises organization.

  • Directory synchronization between your on-premises and Exchange Online organizations.

  • Single sign-on to mailboxes located either on-premises or in the Exchange Online organization.

  • Secure mail routing between on-premises and Exchange Online organizations.

  • Free/busy and calendar sharing between on-premises and Exchange Online organizations.

Even if you plan to permanently move your on-premises email organization to Exchange Online and Office 365 over a longer period of time, you can take advantage of these hybrid deployment features during the transition.

NoteNote:
You have to implement a hybrid deployment to migrate more than 2,000 Exchange 2010 or Exchange 2013 mailboxes to Exchange Online.

To learn more about hybrid deployments, see Exchange Server 2013 Hybrid Deployments. For instructions about moving mailboxes using a remote move migration, see Move mailboxes between on-premises and Exchange Online organizations in 2013 hybrid deployments.

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In a staged Exchange migration, mailboxes in your on-premises Exchange organization are migrated to Exchange Online in batches. A staged Exchange migration is a good option if your current on-premises email organization and migration goals meet the following conditions:

  • You want to permanently move your entire email organization to Office 365.

  • You plan to migrate mailboxes to Exchange Online over a few weeks or months.

  • You plan to manage user accounts in your on-premises organization and synchronize your on-premises Active Directory with Exchange Online.

  • Your current on-premises email organization is Exchange 2003 or Exchange 2007. Staged migration doesn't support migrating Exchange 2010 or Exchange 2013 mailboxes.

  • Your on-premises Exchange organization has more than 2,000 mailboxes.

For an overview of how the staged migration process works, see Staged Exchange migration. For step-by-step procedures, see Migrate mailboxes to Exchange Online with a staged migration.

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In a cutover Exchange migration, all mailboxes in your on-premises Exchange organization are migrated to Exchange Online in a single migration batch. Global mail contacts and distribution groups are also migrated. A cutover Exchange migration is a good option if your current on-premises email organization and migration goals meet the following conditions:

  • You plan to move your entire email organization to Office 365 and manage user accounts in Office 365.

  • You plan to migrate mailboxes to Exchange Online over a few days.

  • Your current on-premises email organization is Exchange 2003 or a later version.

  • Your on-premises Exchange organization has fewer than 2,000 mailboxes.

For an overview of how the cutover migration process works, see Cutover Exchange migration. For step-by-step procedures, see Migrate all mailboxes to Exchange Online with a cutover migration.

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In an IMAP migration, the contents of users' mailboxes on an IMAP messaging system are migrated to their Exchange Online mailboxes. Here are some requirements and considerations for using an IMAP migration:

  • The Exchange Online mailboxes that you migrate email to must already exist. They aren’t provisioned during the IMAP migration process.

  • Only items in a user's inbox or other mail folders are migrated. Contacts, calendar items, or tasks aren't migrated.

  • Small and medium-sized organizations can use an IMAP migration to migrate email from mailboxes on a hosted service provider.

For an overview of how the IMAP migration process works, see IMAP migration. For step-by-step procedures, see Migrate Email from an IMAP Server to Exchange Online Mailboxes.

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Which migration method is right for your organization? It depends on your existing email organization, how many mailboxes you want to migrate, and whether you want to manage user accounts in your on-premises Exchange organization or in Office 365.

Use the following table to decide what type of migration works for your organization.

 

Existing organization Number of mailboxes to migrate Do you want to manage user accounts in your on-premises organization? Migration type

Exchange 2013, Exchange 2010, Exchange 2007, or Exchange 2003

Less than 2,000 mailboxes

No

Cutover Exchange migration

Exchange 2007 or Exchange 2003

Less than 2,000 mailboxes

No

Staged Exchange migration

Exchange 2007 or Exchange 2003

More than 2,000 mailboxes

Yes

Staged Exchange migration or remote move migration in an Exchange hybrid deployment

Exchange 2013 or Exchange 2010

More than 2,000 mailboxes

Yes

Remote move migration in an Exchange hybrid deployment

Exchange 2000 Server or earlier versions

No maximum

Yes

IMAP migration

Non-Exchange on-premises messaging system

No maximum

Yes

IMAP migration

A good way to determine which migration type to use to migrate mailboxes to Exchange Online is by using the Exchange Server 2013 Deployment Assistant. It's a web-based tool that helps you deploy Exchange 2013 in your on-premises organization, configure an Exchange hybrid deployment between your on-premises and Office 365 organizations, or migrate on-premises mailboxes to Office 365. The Deployment Assistant asks you a small set of questions and then, based on your answers, provides instructions to deploy and configure Exchange 2013 in an on-premises hybrid deployment, or migrate mailboxes to Office 365.

To use the Deployment Assistant to help you select a migration type, click Cloud Only in the Exchange 2013 Deployment Assistant and answer a few questions about your current environment. Then, the Deployment Assistant will determine the best option to migrate on-premises mailboxes to Exchange Online.

If the cloud-only option doesn't support your existing Exchange deployment or your organization's needs, click Hybrid, answer a few questions about your current environment, and the Deployment Assistant will generate a list of hybrid deployment instructions for you.

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Most of the email migration support built for Microsoft Office 365 for enterprises assumes that you’re running a version of Exchange in your on-premises organization. This topic is written for organizations that are using Active Directory to manage user resources, but aren’t running Exchange Server on-premises. The goal is to support cross-premises email coexistence. A third-party mail system (IBM Lotus Notes, Novell GroupWise, and so on) remains in the on-premises organization and shares an email namespace with the Microsoft Exchange Online messaging system in the cloud.

 
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