Introduction

With the ever-increasing use of cloud computing, more and more businesses are making the switch to Office 365 for its cloud-based communication, collaboration and productivity abilities.Microsoft 365 or Office 365 supports several methods to migrate email, calendar, and contact data from your existing messaging environment to Microsoft 365 or Office 365

In this article we are going to see Office 365 Migration types available for Exchange to o365

Factors to Consider When Choosing an Office 365 Migration Type

When it’s time to choose between Office 365 migration types, below are the factors we need to consider before proceeding,

• How much time do you need to migrate?
• How big is your migration budget?
• How much data do you need to migrate?
• Which existing email system are you using?
• Which version of Exchange Server are you using?

Types of migrations

• Staged migration
• Hybrid migration
• Cutover migration
• IMAP migration

Staged Migration

As the name suggests, staged migration is a method in which the accounts are split into batches before moving to Office 365. This is done over an extended period. Consider using staged migration in the following cases.

• There are over 2000 mailboxes
• You are using the legacy Microsoft Exchange Server 2003 or Microsoft Exchange Server 2007
• You are experiencing unexplained failures while migrating a large number of mailboxes and splitting them into batches improves the chances of success
• The email migration is complex, and end-users cannot be disrupted with tight deadlines

How to do staged migration in Office 365

• Synchronize the existing users with Office 365 using AD sync
• Generate a CSV list of all the accounts to be migrated
• Create a batch to move email, contacts, and calendar items to Office 365 and convert the existing accounts to Office 365 mailboxes
• Repeat the last two steps for every batch

Advantages of staged migration in Office 365

• Maximum flexibility in moving the accounts
• Minimizes the chances of being stuck with tight deadlines
• Reduces disruption of major business services for end-users
• The batch sizes can be managed for optimal performance

Disadvantages of staged migration in Office 365

• Need to be planned because of the complexity
• A dedicated administrator has to be actively involved throughout the process
• Out of Office messages are not migrated with user mailboxes

Hybrid migration

Some organizations might have to retain their on-premises servers while simultaneously moving to the cloud-based Office 365 services. Such a scenario can arise wherein admin wants to manage their AD accounts on on-premise while users can use Office 365 mailbox and services on the cloud.
One of the greatest benefits of MRS-based moves is that we don’t need to recreate Outlook profiles and re-download the OST after migration, because we keep the same ExchangeGuid and mailbox signature of the mailbox when it is moved. With hybrid remote moves, we migrate all the data that is contained in the mailbox and we cannot skip any data (like dumpster or junk folder)

How to do hybrid migration in Office 365

Hybrid migration is a slightly more complicated process and is best outsourced to experts due to the complexities involved. There are several pre-requisites for the hybrid deployment most important of which is the version compatibility of the Exchange servers. The Office 365 subscription must include Azure Active Directory synchronization to support hybrid deployments. Then the appropriate permissions should be available for the deployment. The generic steps for hybrid migration could include:

• Creation of remote migration endpoints
• Enabling MRSProxy service for on-premises exchange servers
• Use remote move migration type for moving on-premises mailboxes to Exchange Online and complete the migration batches
• Enable offline access for web Outlook
• Advantages of hybrid migration in Office 365
• Secure connection between on-premises and Office 365 accounts
• Shared domain name, calendar, username and password for both accounts
• Integrated control for on-premises and Office 365 accounts
• Message tracking, MailTips, and multi-mailbox search features for both accounts
• Office 365 archiving features extensibility to on-premises Exchange mailboxes
• Free/busy information sharing is possible both ways.

Disadvantages of hybrid migration in Office 365

• Creates avoidable complications due to the concurrent existence of mailboxes
• Necessity to use Azure Active Directory and Office 365 password syncing
• Compulsion to keep the legacy Exchange servers active for longer periods

Cutover migration

A cutover migration is the simplest method to move mailboxes to Office 365. It is similar to staged migration except for the fact that all mailboxes are moved at once. Needless to say, the number and size of mailboxes are significantly smaller while opting for cutover migration.

How to do cutover migration in Office 365

• Create a security group in Office 365 for the new mailboxes
• Connect the servers of the existing system with Office 365
• Move mailbox items to Office 365
• Re-route incoming mails by changing DNS records
• Confirm migration completion

Advantages of cutover migration in Office 365

• One of the simplest migration types available
• Can be done within a few days
• Compatibility with legacy Exchange servers starting with Exchange 2003
• No need for syncing passwords
• Distribution groups, contacts, and other items are also migrated

Disadvantages of cutover migration in Office 365

• Less flexibility in terms of selectively moving objects and mailboxes
• Extensive manual configuration requirements on individual desktops
• No Azure Active Directory synchronization between on-premises servers and Office 365

IMAP Migration

While the other three Office 365 migration types depend solely on Exchange, an IMAP (Internet Message Access Protocol) migration allows you to transition users from Gmail or any other email system that supports IMAP migration.

An IMAP migration pulls information from your source mailboxes and hands it over to Office 365. However, IMAP migration doesn’t transition anything other than email. Calendar items, tasks and contacts all stay in the original inbox and have to be migrated manually by the user.

You’ll also have to create a mailbox for each user before initiating the email migration – something other migration types automatically create for you.

IMAP migrations have a limit of 50,000 total mailboxes and 5,000,000 items. And once the migration is complete, any new mail sent to the original mailbox won’t be migrated.

Disadvantages of IMAP migration in Office 365

• You can only migrate items in a user’s inbox or other mail folders. This type of migration doesn’t migrate contacts, calendar items, or tasks.
• You can migrate a maximum of 500,000 items from a user’s mailbox (emails are migrated from newest to oldest).
• The biggest email you can migrate is 35 MB.
• If you limited the connections to your source email system, it’s a good idea to increase them to improve migration performance. Common connection limits include client/server total connections, per-user connections, and IP address connections on either the server or the firewall.

Microsoft reference URL

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