E-Mail Migration Overview

Applies to: Office 365 for professionals and small businesses, Office 365 for enterprises, Live@edu

You can use E-Mail Migration in the Exchange Control Panel to migrate mail from an on-premises messaging system to your cloud-based organization. You can migrate mailboxes and mailbox data from Microsoft Exchange Server 2010, Exchange Server 2007, and Exchange Server 2003, or migrate mailbox data from an IMAP messaging system. Exchange Online provides the following types of migration:

• Cutover Exchange migration
• Staged Exchange migration
• IMAP e-mail migration
• Compare the types of migration

Microsoft Live@edu: If your institution is using Hotmail as part of the Live@edu experience, you may be able to migrate your e-mail organization to Outlook Live. For more information, see Hotmail to Outlook Live Migration for Live@edu.

Cutover Exchange migration

Use E-mail Migration to provision new cloud-based mailboxes and then migrate mailbox data to the cloud from your on-premises Exchange server. This type of migration is called a cutover because all on-premises mailboxes are migrated in preparation for moving your entire e-mail organization to the cloud. The contacts and distribution groups in your on-premises organization are also migrated. You can migrate a maximum of 1,000 mailboxes from your on-premises Exchange organization to the cloud.

If you have a Microsoft Office 365 e-mail organization, you must assign licenses to new mailboxes or they will be disabled when the grace period ends. For more information, see Assign a License to New Mailboxes in Office 365.

How the cutover Exchange migration process works

Here's an overview of the cutover Exchange migration process. For step-by-step instructions, see Migrate All Mailboxes to the Cloud with a Cutover Exchange Migration.

Important   Before you run an Exchange migration, your on-premises Exchange organization must be an accepted domain of your cloud-based e-mail organization.

1. Start a new migration using E-Mail Migration and select one of the following Exchange migration types:
   • Exchange 2007 and later versions - Automatically detect connection settings with Autodiscover.
   • Exchange 2003 and later versions - Manually specify connection settings.
2. After the migration service verifies the connection settings to your on-premises Exchange server and you run the migration, Microsoft Exchange does the following:
   • It uses the address book from your on-premises Exchange server to identify the mailboxes, distribution groups, and contacts you want to provision in your cloud-based e-mail organization.
   • It provisions the new cloud-based mailboxes. Microsoft Exchange processes up to N migrations at one time, where N is the maximum number of mailboxes to migrate simultaneously that the administrator specified for the migration.
   • It creates distribution groups and contacts. ** The group membership from on-premises groups is recreated for the corresponding cloud-based group. If an on-premises mailbox fails to be migrated, that user can't be added to a cloud-based distribution group. When that mailbox is successfully migrated in a subsequent migration, the user will be added to the group.
   • It migrates mailbox data, which includes e-mail messages, contacts, and calendar items, to the new cloud-based mailboxes. This is called initial synchronization.
3. After the initial synchronization process and mailboxes are successfully provisioned and migrated, the mailboxes in the on-premises Exchange organization and the corresponding cloud-based mailboxes are synchronized every 24 hours. This is called incremental synchronization. This means that any new messages sent to the mailboxes on the Exchange server are copied to the corresponding cloud-based mailboxes. Incremental synchronization continues until the administrator completes the overall migration.
   Note   During incremental synchronization, deletions made in an on-premises mailbox are synchronized to the corresponding cloud-based mailbox. This means that if a user deletes an item from the on-premises mailbox that was previously migrated to the cloud, it will be deleted from the cloud-based mailbox.
4. When the migration is done running, Microsoft Exchange sends a status e-mail message to the administrator. A migration is done when all migration requests are either completed or failed. The status e-mail message includes links to the following CSV files:
   • MigrationErrors.csv, which contains information about each mailbox that failed migration.
   • MigrationStatistics.csv, which contains information about the number of items migrated from each on-premises mailbox. This file also contains an auto-generated, 8-character alpha-numeric password for each mailbox that was migrated. Users are required to reset this password when they log on the first time.
5. Addition migration batches are started, if necessary. The migration service will skip any on-premises mailboxes, contacts, or distribution groups that have already been migrated.
6. After all mailboxes have been successfully migrated, the administrator updates the organization's MX record to point to their cloud-based e-mail organization so that e-mail messages are delivered directly to users' cloud-based mailboxes.
7. After the change to the MX record has been propagated, the administrator completes the migration process. Microsoft Exchange does the following to complete the migration:
   • It runs a final synchronization for all mailboxes. After this, e-mail sent to the on-premises mailboxes is no longer copied to cloud-based mailboxes.
   • It sends a final status e-mail message after the migration is complete.

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Staged Exchange migration

As an alternative to a cutover Exchange migration, you can use E-mail Migration and a CSV file to migrate a subset of your on-premises mailboxes to the cloud. This process is a called staged Exchange migration. This type of migration allows you to maintain short- or long-term coexistence between your on-premises and cloud-based e-mail organizations. In this scenario, you can migrate some mailboxes to the cloud while maintaining the rest of the mailboxes in your on-premises mail environment.

Note   You can’t use a staged Exchange migration to migrate Exchange 2010 mailboxes. Additionally, this migration type is not available in Microsoft Office 365 for professionals and small businesses.

Using a staged Exchange migration, you can migrate user mailboxes and resource mailboxes only. Other recipient types, such as distribution groups, contacts, and mail-enabled users are migrated to Office 365 through the process of directory synchronization.

Important   To use a staged Exchange migration, you have to replicate user objects from your on-premises Active Directory directory service to your cloud-based e-mail organization. Depending on your organization type, you have to install and configure a directory synchronization tool before you can run a staged Exchange migration:

• Microsoft Live@edu   Use Outlook Live Directory Sync (OLSync). For more information, see Implement Outlook Live Directory Sync for Live@edu.
• Microsoft Office 365 for enterprises   Use the Microsoft Online Services Directory Synchronization tool (DirSync). For more information, see Active Directory synchronization: Roadmap.
  Important   After your on-premises mailboxes are migrated to the cloud, the synchronization process continues to update the user attributes on the mailbox according to changes made in the on-premises Active Directory. This means that the “source of authority” for managing user objects is your on-premises directory, and that you can’t manage user mailbox properties in Exchange Online. But after you perform a staged Exchange migration, you can configure the Microsoft Online Services Directory Synchronization tool so that the source of authority is the Office 365 directory. This lets you manage mailbox properties in Exchange Online. For more information, see:
  • Plan for User Identity in a Staged Exchange Migration
  • Directory synchronization and source of authority

How the staged Exchange migration process works

Here's an overview of the staged Exchange migration process. For step-by-step instructions, see Migrate Mailboxes to the Cloud with a Staged Exchange Migration.

1. Install and configure OLSync or DirSync for your cloud-based organization.
2. Create a CSV file that contains a row for each on-premises mailbox that you want to migrate to the cloud. For more information, see Prepare a CSV File for a Staged Exchange Migration.
3. Start a new migration using E-Mail Migration and select one of the following Exchange migration types:
   • Exchange 2007 and later versions - Automatically detect connection settings with Autodiscover
   • Exchange 2003 and later versions - Manually specify connection settings
4. After you provide the connection settings to your on-premises Exchange organization, the migration service does the following:
   • Tests the connection settings to your on-premises Exchange server
   • Verifies that OLSync or DirSync is enabled, depending on your organization type
   • Prompts you to submit a staged migration CSV file
   • Checks that a mail-enabled user (MEU) exists in the cloud-based e-mail organization for each entry in the CSV file
   • Converts the MEU to a mailbox
   • Configures mail forwarding by populating the TargetAddress property on the on-premises mailbox with the e-mail address of the cloud-based mailbox
5. After it creates and configures the cloud-based mailboxes, the migration service e-mails a report that lists the cloud-based mailboxes that were successfully created. At this point, you can tell users to start using their new cloud-based mailbox.
6. The migration service then migrates e-mail messages, contacts, and calendar items from the Exchange mailboxes to the corresponding cloud-based mailboxes.
7. E-mails a final report when the data migration is complete.
8. Addition migration batches and their corresponding CSV migration file are created and started, if necessary.
9. After all on-premises mailboxes have been successfully migrated to the cloud, you can update your organization's MX record to point to your cloud-based e-mail organization so that e-mail messages are delivered directly to users' cloud-based mailboxes.
10. After the change to the MX record has been propagated, you complete the migration process. The migration service does the following to complete the migration:
    • Cleans up any records relating to the previous migration
    • Checks to see if there are any MEUs in your cloud-based organization that correspond to on-premises mailboxes that haven't been migrated to the cloud and displays a warning message
    • Sends a final status e-mail message after the migration is complete

IMAP e-mail migration

You can use E-Mail Migration and a CSV file to migrate the contents of users' mailboxes from an IMAP messaging system to their cloud-based mailbox. This provides organizations with an effective way to move from an IMAP messaging system to a cloud-based e-mail organization. Supported IMAP servers include the following:

• Courier-IMAP
• Cyrus
• Dovecot
• UW-IMAP
• Exchange 2000 Server or previous versions
• Exchange 2003
• Exchange 2007
• Exchange 2010

How the IMAP migration process works

Here's an overview of the IMAP migration process. For step-by-step instructions, see Migrate E-Mail from an IMAP Server to Cloud-based Mailboxes.

1. Create mailboxes in your cloud-based organization for users. For more information, see:
   • Import New Exchange Online Users with a CSV File
   • Create a New Mailbox
2. Create a CSV file that contains a row for each user whose IMAP mailbox you want to migrate. For more information, see Prepare a CSV File to Migrate E-mail from an IMAP Server.
3. Start a new migration using E-Mail Migration and select the IMAP migration type.
4. Configure the migration:
   • Configure the connection settings to the IMAP server.
   • Select folders in the IMAP messaging system to exclude from the migration, such as Deleted Items and Junk Mail or shared and public folders.
   • Submit the CSV file.
5. When you start the migration, Microsoft Exchange does the following:
   • It creates a migration request for each row in the CSV file. Each migration request contains the user name and encrypted password for the account in the IMAP messaging system.
   • It starts processing migration requests. This part of the process is called active mailbox migration or the initial synchronization. For each user listed in the CSV file, messages from the IMAP mailbox are copied to the corresponding cloud-based mailbox until all the mailbox data is migrated. Microsoft Exchange processes up to N migration requests at one time, where N is the maximum number of simultaneous connections that the administrator specified for the migration.
   • It processes the migration requests for all the users included in the CSV file.
6. After the initial synchronization process and mailboxes are successfully migrated, the mailboxes in the IMAP messaging system and the corresponding cloud-based mailboxes are synchronized every 24 hours. This is called incremental synchronization. This means that any new messages sent to the mailboxes on the IMAP server are copied to the corresponding cloud-based mailboxes. Incremental synchronization continues until the administrator completes the overall migration.
   Note   During incremental synchronization, deletions made in an on-premises mailbox are synchronized to the corresponding cloud-based mailbox. This means that if a user deletes an item from the on-premises mailbox that was previously migrated to the cloud, it will be deleted from the cloud-based mailbox.
7. When the migration is done running, Microsoft Exchange sends a status e-mail message to the administrator. A migration is done when all migration requests are either completed or failed. The status e-mail message includes links to the following CSV files:
   • MigrationErrors.csv, which contains information about each mailbox that failed migration. The administrator can fix these errors and resubmit a new CSV file.
   • MigrationStatistics.csv, which contains information about the number of items migrated from each on-premises mailbox.
8. Additional migration batches and their corresponding CSV migration file are created and started, if necessary.
9. After all mailboxes have been successfully migrated, the administrator updates the organization's MX record to point to their cloud-based e-mail organization so that e-mail messages are delivered directly to users' cloud-based mailboxes.
10. After the change to the MX record has been propagated, the administrator completes the migration process. Microsoft Exchange does the following to complete the migration:
    • It runs a final synchronization for all mailboxes. After this, e-mail sent to the mailbox in the IMAP messaging system is no longer copied to cloud-based mailboxes.
    • It sends a final status e-mail message after the migration is complete.

Note As an alternative to using an IMAP migration to migrate mailbox items to cloud mailboxes, you could use the Microsoft Exchange PST Capture tool. PST Capture lets you search for and collect PST files on computers in your on-premises organization and then import the PST files to cloud mailboxes. Note that you can also use PST Capture to import PST files to on-premises primary or archive mailboxes. For more information, see Microsoft Exchange PST Capture.

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Compare the types of migration

Which migration method is right for your organization? It depends on your existing e-mail organization, how many mailboxes you want to migrate, and whether you want to maintain mailboxes in your on-premises organization.

Use the following table to decide what works for your deployment.

Existing organization	Number of mailboxes to migrate	Do you want to maintain mailboxes in your on-premises organization?	Deployment option
Exchange 2010, Exchange 2007, or Exchange 2003	Less than 1,000 mailboxes	No	Cutover Exchange migration
Exchange 2007 or Exchange 2003	No maximum	Yes	Staged Exchange migration or hybrid deployment
Exchange 2010	More than 1,000 mailboxes	No	Hybrid deployment
Exchange 2010	More than 1,000 mailboxes	Yes	Hybrid deployment
Office 365 for professionals and small businesses	Fewer than 50 *	Not applicable **	Cutover Exchange migration
Live@edu	No maximum	Yes	Staged Exchange migration or IMAP e-mail migration
Exchange 2000 Server or previous versions	No maximum	Yes	IMAP e-mail migration
Non-Exchange on-premises messaging system	No maximum	Yes	IMAP e-mail migration

* Office 365 for professionals and small businesses supports a maximum of 50 user mailboxes.

** Office 365 for professionals and small businesses doesn’t support directory synchronization, which is required to maintain mailboxes in your on-premises organization.

What is a hybrid deployment?

If you’re running Office 365 for enterprises and your long-term or short-term goal is to maintain mailboxes both in your on-premises organization and in the cloud, you can deploy Exchange Online into your on-premises organization in what is called a hybrid deployment. In a hybrid deployment, messaging functionality is seamless across the on-premises deployment and the cloud deployment. Features of a hybrid deployment include:

• Moving on-premises mailboxes to the cloud with Mailbox Replication Service (MRS)
• Mail routing between on-premises and cloud-based organizations
• Unified global address list, also called a “shared address book”
• Free/busy and calendar sharing between on-premises and cloud-based organizations
• Message tracking, MailTips, and multi-mailbox search between on-premises and cloud-based organizations

For more information, see Exchange Hybrid Deployment and Migration with Office 365.