100 Days of Cloud – Day 77: Migration Options from On-Premise to Microsoft 365

Its Day 77 of my 100 Days of Cloud journey, and as promised todays post is taking a closer look at the different migration options available to you for moving your on-premise Email workloads to Microsoft 365.

In the last post, we saw the first of those options where we discovered how Exchange Hybrid configuration works. However, this also ties you into keeping an Exchange Server active in your on-premise environment, which for the majority of businesses is costly and negates one of the main drivers of migration: removing the management and cost overhead of maintaining an on-premise email environment.

Migration Options

You can migrate all email, calendar items, tasks and contacts from user mailboxes to Office 365 from an existing on-premises Exchange Server environment.

The available methods are cutover, staged, and Exchange Hybrid migrations. These migration methods copy over all mail data, including contacts, calendar items, and tasks.

You can also use (IMAP) migration from Exchange servers, and if your Exchange server is older than Exchange 2003, or if your on-premise email system is a non-Exchange system. However, you need to be aware that an IMAP migration will copy over only email data.

We’ve already see how Exchange Hybrid works, lets take a look at the other 2 options.

Cutover Migration

A cutover migration moves all of your mailboxes at one time in a single batch. This sort of Office 365 migration process can be used if the email infrastructure runs on Exchange versions from 2003 to 2013.

  • You can move your entire email organization to Microsoft 365 or Office 365 over a few days and manage user accounts in Microsoft 365 or Office 365.
  • A maximum of 2,000 mailboxes can be migrated to Microsoft 365 or Office 365 using a cutover Exchange migration. However, it is recommended that you only migrate 150 mailboxes at a time.
  • The primary domain name used for your on-premises Exchange organization must be an accepted domain owned by you in your Microsoft 365 or Office 365 organization.
  • After the migration is complete, each user who has an on-premises Exchange mailbox also will be a new user in Microsoft 365 or Office 365. However, you must still assign licenses to users whose mailboxes are migrated.

After your on-premises and Microsoft 365 or Office 365 organizations are set up for a cutover migration, post-setup tasks could impact your users.

  • Administrators or users must configure desktop computers to ensure these are set up for use with Microsoft 365 or Office 365.
  • Potential delay in email routing until the MX record is changed from on-premise to Microsoft 365.

The steps needed to run a cutover migration are shown in the image below:

Image Credit: Microsoft
  1. The administrator communicates upcoming changes to users and verifies domain ownership with the domain registrar.
  2. The administrator prepares the servers for a cutover migration and creates empty mail-enabled security groups in Microsoft 365 or Office 365.
  3. The administrator connects Microsoft 365 or Office 365 to the on-premises email system (this is called creating a migration endpoint).
  4. The administrator migrates the mailboxes and then verifies the migration.
  5. Grant Microsoft 365 or Office 365 licenses to your users.
  6. The administrator configures the domain to begin routing email directly to Microsoft 365 or Office 365.
  7. The administrator verifies that routing has changed, and then deletes the cutover migration batch.
  8. The administrator completes post-migration tasks in Microsoft 365 or Office 365 (assigns licenses to users and creates an Autodiscover Domain Name System (DNS) record), and optionally decommissions the on-premises Exchange servers.
  9. The administrator sends a welcome letter to users to tell them about Microsoft 365 or Office 365 and to describe how to sign in to their new mailboxes.

Further detail on how Cutover Migration works can be found here.

Staged Migration

For Exchange server versions running either 2003 or 2007, the only supported migration method to Microsoft O365 is Staged Migration. With this migration type, you can move your entire email infrastructure in batches. This method is beneficial for legacy Exchange servers if you have more than 2000 seats; however, for a successful migration, some critical factors need to be taken into consideration:

  • You must synchronize accounts between your on-premises Active Directory domain and Microsoft 365 or Office 365 by using Azure Active Directory sync for a staged migration to work.
  • The primary domain name used for your on-premises Exchange organization must be a domain verified to your Microsoft 365 or Office 365 organization.
  • You can migrate only user mailboxes and resource mailboxes. Other recipient types, such as distribution groups, contacts, and mail-enabled users are migrated to Microsoft 365 or Office 365 through the process of directory synchronization.
  • Out of Office messages aren’t migrated with user mailboxes. The user needs to recreate the Out of Office message after the mailbox is migrated.
  • If you limited the connections to your source email system, it’s a good idea to increase them to improve migration performance.

The steps needed to run a staged migration are shown in the image below:

Image Credit: Microsoft
  1. The administrator synchronizes the list of users between their on-premises environment and Microsoft 365 or Office 365.
  2. The administrator creates a comma-separated value (CSV) file that contains a row for each user whose on-premises mailbox will be migrated in the migration batch.
  3. The administrator creates and runs a staged migration batch by using the migration dashboard in the Exchange admin center.After the administrator starts the migration batch, Exchange Online does the following:
    • Verifies that directory synchronization is enabled.
    • Checks that a mail-enabled user exists in the Microsoft 365 or Office 365 organization for each user listed in the CSV file. Mail-enabled users are created in Microsoft 365 or Office 365 as a result of the directory synchronization process.
    • Converts the Microsoft 365 or Office 365 mail-enabled user to an Exchange Online mailbox for each user in the migration batch.
    • Begins initial synchronization. Exchange Online processes up to N migration requests at one time. N represents the maximum number of concurrent migrations that the administrator specified when creating the migration endpoint used for the migration batch. By default, initial synchronization is performed on 20 mailboxes at a time until all mailboxes in the migration batch are migrated.
    • Configures mail forwarding. The TargetAddress property on the on-premises mailbox is configured with the email address of the Exchange Online mailbox. This process means that mail sent to the on-premises mailbox is forwarded to the corresponding Exchange Online mailbox.
  4. After it creates the Exchange Online mailbox and configures mail forwarding for each user in the CSV file, Exchange Online sends a status email message to the administrator. This status message lists the number of mailboxes that were successfully migrated and how many couldn’t be migrated. The message also includes links to migration statistics and error reports that contain more detailed information. At this point, users can start using their Exchange Online mailboxes.
  5. As part of initial synchronization, Exchange Online then migrates all email messages, contacts, and calendar items from the on-premises mailboxes to Exchange Online mailboxes. Exchange Online sends a final migration report when the data migration is complete.
  6. After a migration batch is complete and the administrator verifies that all mailboxes in the batch are successfully migrated, the administrator can convert the on-premises mailboxes to mail-enabled users.
  7. If a user opens their mailbox with Outlook, the Autodiscover service tries to connect to the on-premises mailbox. After you convert on-premises mailboxes to mail-enabled users, the Autodiscover service uses the mail-enabled user to connect Outlook to the Exchange Online mailbox after the user creates a new Outlook profile.
  8. The administrator creates additional migration batches, submitting a CSV file for each one.
  9. The administrator runs additional migration batches.
  10. The administrator resolves any issues. After all on-premises mailboxes in a batch are successfully migrated, the administrator deletes the migration batch.
  11. Users can use their Exchange Online mailboxes.
  12. The administrator, to complete the transition to Exchange Online and Microsoft 365 or Office 365, performs post-configuration tasks such as:
    • Assign licenses to Microsoft 365 or Office 365 users.
    • Configure the MX record to point to your Microsoft 365 or Office 365 organization so that email is delivered directly to Exchange Online mailboxes.
    • Create an Autodiscover Domain Name System (DNS) record for your Microsoft 365 or Office 365 organization.

Further detail on how Cutover Migration works can be found here.

Conclusion

So thats a look at the different migration options available to migrate your on-premise Exchange environment to Microsoft 365 tenant.

In the next post, we’ll look at the myriad of different licensing options available. Hope you enjoyed this post, until next time!

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