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How to Migrate Exchange Mailbox to Office 365: Step-by-Step Guide [2025]

Admin ~ Modified: July 1st, 2025 ~ Microsoft Exchange Server ~ 6 Minutes Reading

If you need to migrate Exchange mailbox to Office 365, this guide gives you every step you need, no guesswork. I’ll walk you through Cutover, Staged, Hybrid, and automated migration methods. 

Let’s go through:

Why I Chose Exchange Mailbox Migration to Office 365

A few months ago, I realised our on-premises Exchange Server was becoming more of a liability than an asset. Because of manual security updates, hardware maintenance, and storage limitations, I decided to migrate to Office 365 (Microsoft 365). The benefits were obvious:

  • Access anywhere via the cloud
  • Reduced maintenance
  • Built-in security and compliance features
  • Seamless integration with every M365 service like Teams, OneDrive, and SharePoint

How to Migrate Exchange Mailbox to Office 365?

I found four solutions for this migration, and all of them are listed below with their details, instructions: 

Method 1. Cutover Migration (Exchange 2007–2013)

I used this method to migrate Exchange 2013 to Office 365 for fewer than 150 mailboxes. It helps in Exchange mailbox migration to Office 365. 

Pre-requisites

  • Exchange Server 2007 SP3 or later (up to 2013)
  • Less than 150 mailboxes
  • Outlook Anywhere and Autodiscover must be enabled
  • Admin account with full permissions on all mailboxes
  • Valid SSL certificate (not self-signed)
  • Verify your domain in Microsoft 365

Here’s every step I followed to migrate Exchange mailbox to Office 365.

  • Ensure Outlook Anywhere is enabled:

    Get-OutlookAnywhere | FL Server,ExternalHostname,SSLOffloading,ExternalClientsRequireSsl
  • Test Autodiscover:
  • Use https://testconnectivity.microsoft.com (Remote Connectivity Analyzer)
  • Set the admin account with full access:

    Get-Mailbox -ResultSize Unlimited | Add-MailboxPermission -User AdminAccount -AccessRights FullAccess -InheritanceType All
  • Confirm the domain is verified in the Microsoft 365 Admin Center.

Now, configure the migration endpoint in Microsoft 365:

  1. Open Microsoft 365 Admin Center > Exchange Admin Center (EAC)
  2. Navigate to Migration > Endpoints > +
  3. Choose Outlook Anywhere, then enter:
    1. Email
    2. Credentials
    3. Server
  4. In EAC > Migration > + > Migrate to Exchange Online > Cutover
  5. Name the migration batch (e.g., CutoverBatch01)
  6. Select the endpoint created earlier
  7. Add all mailboxes (automatically detected)
  8. Set options for sync time and notifications
  9. Start the batch immediately for Exchange mailbox migration to Office 365
  10. View status in EAC > Migration dashboard
  11. Update your DNS panel with Microsoft 365 values:
    1. MX Record
    2. Autodiscover
    3. SPF TXT Record
  12. Decommission Exchange Server
    1. Remove Exchange from AD
    2. Remove DNS entries pointing to the old Exchange

Method 2. Staged Migration (Exchange 2003 or 2007)

This works well if you have more than 150 mailboxes and are running Exchange 2003 or 2007. It migrates mailboxes in batches over time.

Pre-migration steps:

  • Exchange Server 2003 or 2007
  • Use Azure AD Connect to sync identities
  • Mailboxes in batches (CSV required)
  • Domain verified in Microsoft 365
  • AppPassword or basic auth enabled (if MFA is on)
  • Clean up AD using the IdFix tool
  • Install Azure AD Connect to sync on-prem AD with Microsoft 365
    • Choose Password Hash Sync or Pass-Through Authentication
  • Create a list of mailboxes:
EmailAddress
user1@domain.com
user2@domain.com

Here are the main steps to migrate Exchange Mailbox to Office 365 simultaneously:

  • Open Microsoft 365 EAC > Migration > Endpoints > +
  • Choose Staged Migration
  • Enter:
    • Admin credentials
    • Exchange server FQDN
    • RPC proxy (Outlook Anywhere) settings
  • Now, in EAC > Migration > + > Migrate to Exchange Online > Staged Migration
  • Upload the CSV file
  • Choose your endpoint
  • Configure batch settings and start
  • Once users appear in M365:
  • Go to Microsoft 365 Admin Center > Users > Active Users
  • Assign licenses with Exchange Online enabled
  • As in Cutover migration:
  • MX, Autodiscover, and SPF need to point to Microsoft 365
  • Once all batches are complete and mail flow works, decommission your on-prem Exchange server.

Method 3. Use Hybrid Migration (Exchange 2010+)

I helped another organisation migrate Exchange mailbox to Office 365 with 1000+ mailboxes using this method:

Pre-requisites

  • Exchange 2010, 2013, 2016, or 2019
  • Valid SSL Certificate from a trusted CA
  • Azure AD Connect is configured
  • Federation trust + OAuth between on-prem and Microsoft 365
  • Domains verified in Microsoft 365

Now, follow the steps for Office 365 Hybrid migration: 

  • Install the latest CU on Exchange
  • Ensure external DNS (mail.domain.com) points to Exchange
  • Set up public SSL cert (mail.domain.com, autodiscover.domain.com)
  • Verify the domain in Microsoft 365

Now, install and configure Azure AD Connect

  • Download and install Azure AD Connect
  • Choose Hybrid Identity: Password Hash Sync or PTA
  • Enable the Exchange Hybrid Deployment checkbox during setup

Afterwards, run the Hybrid Configuration Wizard (HCW) to migrate Exchange mailbox to Office 365

  1. Download from Microsoft: aka.ms/HybridWizard
  2. Launch HCW on Exchange Server
  3. Enter Microsoft 365 global admin credentials
  4. Choose Minimal or Full Hybrid
  5. Choose mail flow:
    • Centralised (through on-prem Exchange)
    • Decentralised (directly from Office 365)

Now, for migrating mailboxes, follow these steps:

  1. In Exchange Admin Center > Recipients > Migration > New Migration Batch
  2. Choose Remote Move Migration
  3. Select mailboxes and define an endpoint
  4. Start migration batch
  5. Monitor batch status (Synced > Completed)

Method 4. Automated Exchange Mailbox Migration to Office 365 (No Downtime)

If you are searching for a solution that can migrate Exchange mailbox to Office 365 with no downtime, then MigratorWizard Exchange to Office 365 Migration Tool will be your go-to. 

Download Now Purchase Now

I recommended this solution for these reasons:

  • Automatically maps users
  • Transfers emails, contacts, calendars, tasks, and more
  • Supports Exchange 2010, 2013, 2016, and 2019
  • Ensures zero data loss
  • Includes real-time progress tracking

I moved over 300 mailboxes over a weekend with zero downtime. The tool allowed for selective migration and reran only failed items during retries.

Here’s how I used this tool for transition:

  • Step 1. Run the solution, and select Exchange(source) & Microsoft 365(target) options.

select source & target

  • Step 2. Under workload selection, select Email, Contact, and Calendar. Leverage the Date filter option if needed to migrate specific data.

workload selection

  • Step 3. Now, provide the credentials and Exchange version.

provide the credentials and Exchange version

  • Step 4. In the destination window, provide Admin credentials for the Office 365 account.

provide Admin credentials for the Office 365 account 

  • Step 5. Map the source users via Fetch Users, Import Users, or Download Template.

Map the source users

  • Step 6. After the validation, hit the Start Migration button. 

Migrate Exchange Mailbox to Office 365

Post-Migration Tasks I Performed

After a successful Exchange mailbox migration to Office 365, I made sure to:

  • Inform users and provide new login instructions
  • Recreate Outlook profiles and mobile setups
  • Assign roles and permissions in Microsoft 365
  • Enable archiving and retention policies
  • Set up email forwarding or shared mailboxes if needed

Closing Thoughts

I’ve been through Exchange mailbox migration to Office 365, and with the right planning and appropriate tools, you can make it seamless. If you’re planning to migrate Exchange mailbox to Office 365, then it is suggested to opt for the specified automated tool(Method 4) to complete the task with zero time.  

FAQs on Migrating Exchange to Office 365

Q1. Can I migrate without automated tools?
Yes, using cutover, staged, or hybrid methods, but automated tools greatly reduce time and errors.

Q2. How long does Exchange mailbox migration to Office 365 take?
Depends on the mailbox size and the network. For 100 mailboxes (~2GB each), it took me about 2 days.

Q3. Do I need to reconfigure Outlook for users?
Usually yes, but tools or PowerShell scripts can help automate this.

Q4. What Exchange versions support hybrid migration?
Exchange 2010 and above. You’ll need Azure AD Connect and proper certificates.