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How to Migrate Mailboxes from Exchange to Office 365. Migrating mailboxes from Exchange to Office 365 is a complex process. Especially for organizations with large amounts of data and multiple mailboxes. However, with a proper planning and execution, we migrate seamlessly without disrupting day to day operations.

This article explains with step by step guide on migrating mailboxes from Exchange to Office 365. We cover everything from pre-migration planning and preparation to the migration process and post migration tasks. By following these steps, organizations successfully transition to Office 365 and take advantage of its powerful collaboration and productivity features.

How to Migrate Mailboxes from Exchange to Office 365

Microsoft Exchange is the most widely used mail server and calendaring program. We don’t require special hardware or software because it runs on any machine with the Windows Server op system.

With business class features, Microsoft’s cloud based Exchange Online service provides a hosted email solution. Users access shared calendars, contacts, and emails even while traveling. It is a component of Office 365 Premium.

Importance of Microsft Office 365 Migration

Companies may consider hosting their Exchange services on premises for a variety of reasons. The capacity to manage all hardware and data is one of the most crucial aspects, offering full access for troubleshooting if necessary. However, this process comes at the cost of more extraordinary maintenance expenses and 100% availability.

When we switch from on premise to Office365, we get several essential benefits. Some of them consist of the following:

  • Office 365 provides all the necessary tools for work, with scalability and no additional spending.
  • Purchase includes hosting and email accounts, saving time and installation costs.
  • It only costs once instead of an on-premise server’s expensive running costs and ongoing maintenance.
  • Microsoft ensures the security of data with its disaster recovery plans.
  • In case of an issue, access and control over data are maintained in Settings.

We feel assured knowing that our server is secure and up to date, if we use an automatic update service with no downtime or other such situations.

Migration Exchange to Office 365

Exchange on Microsoft Office 365 Moving our Exchange organization’s email, calendar, and contacts data to the cloud based Office 365 is known as migration. Based on our organization’s current Exchange Server, the number of mailboxes we need to migrate. Whether we want to manage some mailboxes on-premises or migrate them fully online, Microsoft offers 5 migration types. Review and select the best choice for our firm.

Import Service for PST Files Migration

The Microsoft 365 Import Service is helpful, if we want to move our email data from an outdated system. Users with Office 365 accounts and huge PST files easily import PST files into Office 365 using this service. We send our outdated PST files using a network disk or the import service.

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Migrate Mailboxes From Microsoft Exchange Server

There are 3 ways to transfer mailboxes of this sort from Exchange Server to Office 365:

Cutover Migration

Transfers all mailboxes to Office 365 at once. If our Exchange Server is running Exchange 2003/2007/2010/2013 and we have fewer than 2000 users, the cutover migration is a great approach to upgrade it. Additionally, small businesses with email systems that use the Exchange admin center (EAC) use this “migrate to office365” technique. 

Since the process moves quickly and simultaneously, we refer to these frequent Exchange migrations as “cutovers.” Ideal for handling enormous mailboxes, such as those found in large enterprises or government organizations that must complete things quickly before deadlines approach.

Check out the Cutover Migration Step-by-Step Guide below:

  1. Add our domain to Office 365.
  2. Prepare our on-premises environment.
  3. Connect Office 365 to our email system.
  4. Move the mailboxes using a cutover migration batch.
  5. Convert on-premises mailboxes to mail-enabled users.
  6. Configure DNS to reduce email delivery delays.
  7. Route our email directly to Office 365.
  8. Assign Office 365 licenses to our users.
  9. Delete the cutover migration batch as an admin.
  10. Create an Autodiscover record.
  11. Decommission our Exchange servers.
  12. Help users install the updated version of Office on their computers.
  13. Give users the knowledge they require to begin utilizing Office 365.
  14. For a staged migration, migrate mailboxes to Office 365 in batches.

Staged Migration

To prevent downtime, it’s crucial to arrange the users’ mailbox migration from one platform (i.e., source) to another while migrating from Exchange to Office 365. For instance, if we use Microsoft 365 or Office 365, we migrate data in stages rather than all at once, which could take hours, if done correctly.

Instead, the company feeds off subscribers’ Emails as they come through on both systems until we successfully copy everything over. Use staged migration, if we use Exchange 2003/2007 and have more than two thousand (2000) mailboxes. But first, check the Step-by-Step Guide for Staged Migration below:

  1. Visit Exchange Admin Center and navigate to Recipients > Migration.
  2. Click on the New+ icon and select the Migrate to Exchange Online option.
  3. Select the Staged Migration option on the pop-up Migration Type screen and click Next.

4. Choose the desired CSV file for the migration batch.
5. Validate the CSV file for Office 365 verification and click Next.
6. Authenticate the migration endpoint information and click Next.

7. Confirm the migration endpoint information, enter authentication details, and click Next.
8. Verify the migration endpoint information to ensure accuracy.
9. Choose Auto Start and Manual options to start the batch process, and click Start.

10. Click New to create a migration batch.
11. In Exchange Admin Center, select Recipients and choose the appropriate migration options for email accounts.
12. From the Migration dashboard, select a batch and click Start.
13. Check the syncing status on the dashboard to confirm a successful migration.
14. Use an integrated Exchange Server and Office 365 environment for hybrid migration.

Hybrid Migration

Use this migration method if we use Exchange 2010 or later and there are more than 150–2,000 mailboxes. With hybrid migration, we gradually move mailboxes to Office 365 by establishing a connection between the Exchange Server at our company and that service.

IMAP Migration

We move users and emails using this form of migration from email systems like Gmail, Exchange, Outlook, and others that support Internet Message Access Protocol (IMAP). The first step in using an IMAP migration for our users is to add them to our organization’s contact list in Microsoft 365 or Office 365. Check out the Staged Migration Step-by-Step Guide below:

  1. Sign in to the Microsoft 365 admin center.
  2. Go to Setup and select Migrations under Featured Collections.

3. On the Migrations page, select Email and click Get Started.
4. Choose to Import my Email messages in the Email Sources pane.
5. Select our data service dashboard opens.

6. If the provider is listed, select Email Provider and choose users to migrate the Email messages page.
7. Directly send our email to Office 365. Choose Other Email sources if the provider didn’t include them. Please fill up the IMAP connection details to test the connection on the Select our details Service page before clicking Save.
8. To add a user’s email address to our database, check the box next to their name, then make a new password.
9. Select Start Migration. The IMAP migration periodically synchronizes with our source Email account until we choose to Stop Migration.

10. Before ending the batch, we advise you to let it run for at least 72 hours.
11. After finishing the migration, select Close Connection and click Start new migration if desired.

User Initiated Migration

With an easy-to-use interface, users rapidly move their emails, contacts, and mailbox data from one account to another.

FAQs About Exchange to Office 365 Migration

Q: Why should I migrate my mailboxes from Exchange to Office 365? 

A: Office 365 provides various benefits, such as improved collaboration, access to cloud based applications, and simplified management of user accounts. Additionally, Office 365 offers better integration with other Microsoft products and services.

Q: Can I migrate all of my mailboxes at once? 

A: It depends on the size of our organization and the number of mailboxes we have. We recommend migrating a few mailboxes at a time to avoid overwhelming our system and to ensure a smooth migration process.

Q: What should I consider before migrating my mailboxes? 

A: Consider things like the size and complexity of our business, the volume of data we have, the compatibility of our present systems with Office 365, and the resources available for the migration process before converting our mailboxes.

Q: What are some common challenges I may face during migration? 

A: Some common challenges include data loss or corruption, compatibility issues, connectivity problems, and user resistance to change. 

Q: What is the estimated time for the mailbox migration process? 

A: Depending on our organization’s size and complexity, the volume of data we have, and the resources available for the conversion process. Generally speaking, it takes a few days to a few weeks.

Q: Do I need to back up my data before migrating to Office 365? 

A: Yes, we recommend backing up our data before migrating to Office 365 to prevent corruption or data loss during the migration process.

Q: Can I use a third-party tool to migrate my mailboxes to Office 365? 

A: Yes, many third-party tools help with the mailbox migration process. Essential to choose a reputable tool and ensure it’s compatible with our current system and Office 365.

Thank you for reading How to Migrate Mailboxes from Exchange to Office 365. We shall conclude this article now. 

How to Migrate Mailboxes from Exchange to Office 365 Conclusion

In conclusion, migrating mailboxes from Exchange to Office 365 is complex. Still, with careful planning and execution, we seamlessly do it without disrupting day-to-day operations. It’s crucial to consider aspects like our organization’s size and complexity, the volume of data we have, and the resources available for the conversion process. Additionally, to ensure we have a copy of all our data in case any is lost or corrupted during the migration process, we advise backing up our data before the migration.

By following the step-by-step guide and considering these factors, organizations successfully transition to Office 365 and take advantage of its powerful collaboration and productivity features.


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Marion Mendoza

Marion Mendoza

Windows Server and VMware SME. Powershell Guru. Currently working with Fortune 500 companies responsible for participating in 3rd level systems support across the enterprise. Acting as a Windows Server engineer and VMware Specialist.

Comment (1)

  1. charlote
    May 21, 2023

    I use Gs Richcopy 360, it is the best for migrating to Office 365

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