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Ultimate Migrate Exchange to Office 365 (Step by Step Guide)

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.

Ultimate Exchange to Office 365 Migration Guide in 2025

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.

Migrate Exchange to Office 365

Migrate Exchange to Office 365 such 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 3 migration types. Review and select the best choice for your Exchange migration below.

Step 1: Assess Your Current Exchange Environment

Before migrating any mailboxes to Microsoft 365 (formerly Office 365), it’s essential to assess and understand your current on-premises Exchange infrastructure. This step ensures a smooth transition and avoids unexpected compatibility issues, user disruption, or service downtime.

Why This Matters?

Failing to properly assess your environment can lead to:

  • Migration failure due to unsupported configurations

  • Misaligned licensing plans in Microsoft 365

  • Incomplete mailbox moves

  • Delays caused by DNS, networking, or throttling issues

This step also aligns with:

  • CIS Microsoft 365 Foundations Benchmark v1.5: Control 1.1 – “Ensure security and configuration management planning is conducted prior to migration.”

  • NIST SP 800-53 Rev 5: CM-2 – “Baseline Configuration”

What You Should Assess

1. Current Exchange Version Compatibility

Make sure your on-premises Exchange version supports the type of migration you plan:

Exchange VersionSupported Migration Types
Exchange 2010Cutover, Staged, Hybrid
Exchange 2013Cutover, Hybrid
Exchange 2016Hybrid
Exchange 2019Hybrid

Run this command to get your current version:

				
					Get-ExchangeServer | Select Name, Edition, AdminDisplayVersion

				
			

2. Mailbox Count and Sizes

Analyze how many mailboxes are to be migrated and their sizes to estimate timeline and bandwidth.

				
					Get-Mailbox -ResultSize Unlimited | Get-MailboxStatistics | Select DisplayName, TotalItemSize, ItemCount

				
			

3. Autodiscover and Outlook Anywhere Configuration

Ensure both services are correctly configured and reachable externally.

Test Outlook Anywhere:

				
					Test-OutlookConnectivity -Protocol HTTP -RunFromServerId <YourServer> -TargetEmailAddress <test-user@domain.com>

				
			

4. Networking and Firewall Rules

  • Ensure ports 443 (HTTPS) and 80 (HTTP) are open.

  • Validate access to outlook.office365.com, autodiscover.outlook.com, and Exchange Web Services (EWS).

5. SMTP and MX Record Configuration

You’ll eventually change your MX records to point to Microsoft 365, but you should verify where they’re currently pointing using:

				
					nslookup -q=mx yourdomain.com

				
			

Exchange Migration Preparation Tools

Step 2: Choose the Migration Method (Cutover, Staged, or Hybrid)

Choosing the right migration strategy is critical to ensuring a successful and efficient mailbox transition from your on-premises Exchange environment to Microsoft 365. Each method has different use cases, technical requirements, and business implications.

Why This Step Is Important

Selecting the wrong migration method can:

  • Cause delays due to unsupported Exchange versions

  • Create user confusion or mail flow issues

  • Lead to unnecessary costs or licensing changes

This step helps satisfy:

  • CIS Microsoft 365 Foundations Benchmark v1.5: Control 1.2 – “Establish a secure and managed onboarding strategy for cloud applications and services.”

  • NIST SP 800-53 Rev 5: SA-8 – “Security and Privacy Engineering Principles”

Overview of Microsoft 365 Mailbox Migration Methods

MethodBest ForExchange Versions SupportedUser LimitDowntime
CutoverSmall orgs (<150 users)2010, 2013, 2016Up to 150Short window
StagedMedium orgs (150–2,000 users)2003, 2007 (hybrid not possible)Up to 2,000Some
HybridLarge orgs / co-existence2010, 2013, 2016, 2019UnlimitedNone

1. Cutover Migration

What is it?
Migrates all mailboxes and Exchange components in a single batch to Microsoft 365. Best for small organizations.

Requirements:

  • Exchange 2010+ (does not support Exchange 2003/2007)

  • Single forest, single domain

Pros:

  • Simple setup

  • Fast migration (few days)

Cons:

  • No coexistence between on-prem and cloud

  • Requires DNS record switch at time of cutover

2. Staged Migration

What is it?
Moves mailboxes in batches over time. Best for organizations still on Exchange 2003 or 2007 or that need more flexibility during the migration.

Requirements:

  • Exchange 2003 or 2007

  • Directory synchronization set up via Azure AD Connect

Pros:

  • Transition over multiple days or weeks

  • Less user disruption

Cons:

3. Hybrid Migration

What is it?
Provides seamless coexistence between your on-prem Exchange and Microsoft 365. Allows you to gradually migrate mailboxes.

Requirements:

  • Exchange 2010 or newer

  • Azure AD Connect

  • Hybrid Configuration Wizard

Pros:

  • No disruption to end users

  • Enables single sign-on (SSO)

  • Unified GAL (Global Address List)

Cons:

  • Requires certificate-based secure mail flow

  • More complex configuration

How to decide which Exchange to Office 365 Migration Method to Use?

QuestionRecommended Option
Do you have fewer than 150 users?Cutover
Are you using Exchange 2003/2007?Staged
Do you want mailbox coexistence or plan to keep hybrid for long term?Hybrid

Step 3: Prepare Exchange Migration (DNS, Licensing, Security & More)

Before initiating any mailbox migration, it’s critical to prepare your Microsoft 365 and Exchange environments to ensure a secure and seamless process. This includes DNS readiness, licensing, authentication setup, and verifying permissions. Skipping this step is one of the most common causes of migration failures.

Why This Step Is Important

Improper preparation may result in:

  • Failed mailbox moves

  • Broken Autodiscover or Outlook connectivity

  • Login or authentication errors

  • Delays due to missing licenses or permissions

This step supports:

  • CIS Microsoft 365 Foundations Benchmark v1.5:

    • Control 1.3“Ensure a baseline configuration is defined for cloud resources.”

    • Control 1.5“Ensure secure DNS and identity services are configured.”

  • NIST SP 800-53 Rev 5:

    • AC-2(5)“Privileged account access review before deployment”

    • SC-12“Cryptographic Key Establishment”

1. Validate Domain in Microsoft 365

Before migration, your on-prem domain (e.g., yourdomain.com) must be verified in Microsoft 365 Admin Center.

🔹 Go to: admin.microsoft.com → Settings → Domains
🔹 Add your domain and verify it using the TXT record provided.

PowerShell Command to check domains:

				
					Connect-MgGraph -Scopes "Directory.Read.All"
Get-MgDomain

				
			

2. Configure Autodiscover and DNS Records

Ensure that your Autodiscover DNS record is correctly pointing to your on-prem Exchange (for hybrid) or Microsoft 365 (after migration).

Required DNS Records for Office 365:

Record TypeHostPoints toPurpose
TXT@MS=xxxxxxxDomain verification
MX@domain-com.mail.protection.outlook.comMail flow
CNAMEautodiscoverautodiscover.outlook.comAutodiscover
CNAMEsipsipdir.online.lync.comSkype/Teams login
SRV_sip._tlssipdir.online.lync.comSkype/Teams service

Check your current DNS:

				
					nslookup -type=mx yourdomain.com

				
			

3. Assign Office 365 Licenses

Each mailbox to be migrated requires a valid Office 365 license with Exchange Online included (e.g., Business Standard, E3, or E5).  Licenses must be assigned before mailbox migration, Why ?

  1. Exchange Online Mailbox Creation:
    Microsoft 365 will only create a cloud mailbox after a license with Exchange Online is assigned. Without this license:

    • Migration batch will fail

    • No target mailbox exists to receive migrated data

  2. Directory Sync Dependencies (for Staged/Hybrid):
    If using Azure AD Connect (Hybrid or Staged migrations), synced users appear in Microsoft 365 but won’t have mailboxes until a license is applied.

What Happens If You Don’t Assign a License?

  • The migration batch throws an error:
				
					A cloud mailbox does not exist for user@domain.com. Assign a license before proceeding.

				
			
  • For staged/hybrid migrations, mailbox provisioning will not complete until licensing is resolved.

Best Practice Workflow

StepAction
1Sync users to Microsoft 365 (if applicable)
2Assign license with Exchange Online to each target user
3Wait a few minutes (~15–30 mins) for the mailbox to provision
4Start mailbox migration

PowerShell Example to assign a license:

				
					Connect-MgGraph -Scopes "User.ReadWrite.All"
Set-MgUserLicense -UserId user@domain.com -AddLicenses @{SkuId='ENTERPRISEPACK'}

				
			

Check unlicensed users:

				
					Get-MgUser -Filter "AssignedLicenses eq null"

				
			

4. Set Up Authentication (MFA, SSO, Conditional Access)

Prepare users for identity changes by enabling secure authentication methods:

  • MFA (Multi-Factor Authentication): Enforce for all users and admins

  • SSO (Optional): If using hybrid identity via Azure AD Connect

  • Conditional Access Policies: Block legacy protocols, restrict logins by country/IP

CIS Benchmark Control Mappings:

  • Control 2.3.1“Ensure Modern Authentication is enabled”

  • Control 2.6.1“Ensure MFA is enabled for all users”

PowerShell (Graph SDK) to check MFA state:

				
					Get-MgUserAuthenticationMethod -UserId user@domain.com

				
			

5. Grant Mailbox Permissions and Test Access

Ensure the admin account running the migration has:

  • ApplicationImpersonation role

  • FullAccess permissions (for hybrid/staged)

PowerShell to assign impersonation:

				
					New-ManagementRoleAssignment -Role "ApplicationImpersonation" -User MigrationAdmin

				
			

Test Mailbox Access:

				
					Test-Mailbox -Identity "user@domain.com"

				
			

6. Directory Sync (Hybrid or Staged Only)

Install and configure Azure AD Connect to sync your on-prem AD users with Microsoft 365.

Verify Sync Status:

				
					Get-MsolUser -Synchronized

				
			

7. Plan for Downtime and User Communication

Prepare for:

  • Possible short downtime during cutover

  • Informing users of new login procedures

  • Setting up redirection for Outlook profiles

Create a communication plan that includes:

  • Migration date and expected downtime

  • Login instructions post-migration

  • FAQs and support contact

Step 4: Execute the Migration (Cutover, Staged, Hybrid)

Now that you’ve assessed your environment and completed pre-migration tasks, it’s time to begin migrating mailboxes. This step walks you through how to execute a mailbox migration using Cutover, Staged, or Hybrid methods — via both the Microsoft 365 GUI and PowerShell commands.

Why This Step Is Critical

Improperly executing your migration can result in:

  • Incomplete or failed mailbox moves

  • Email downtime or mail loss

  • Broken Outlook profiles

  • Missed compliance expectations

This step supports:

  • CIS Microsoft 365 Foundations Benchmark v1.5:

    • Control 1.6“Ensure secure transition to cloud services with validated testing.”

  • NIST SP 800-53 Rev 5:

    • SI-2(6)“System and Communications Protection – Migration Testing and Validation”

A) Execute a Cutover Migration

Best for: Small organizations with <150 mailboxes
Supported Exchange Versions: Exchange 2010, 2013, 2016
Unsupported: Exchange 2003, 2007, or hybrid deployments
Tools Required: Exchange Admin Center (EAC), Microsoft 365, Outlook

Office 365 cutover migration
Office 365 Cutover Migration Flow

A cutover migration transfers all mailboxes to Office 365 at once.  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.

1. Verify prerequisites:

  • Domain is verified in Microsoft 365

  • Autodiscover is working externally

  • Admin account has full access to all mailboxes

2. Prepare Exchange for Migration:

  • Ensure all mailboxes are visible to the admin account

  • Disable Unified Messaging if enabled

3. In Microsoft 365 Admin Center:

  1. In the Exchange admin center, go to Migration, and select Add migration batch.

2. On the Add migration batch page,

  • Give migration batch a unique name: Type a migration name, for example, HR_Migration2.
  • Select the mailbox migration path: Verify that Migration to Exchange Online is selected.

3. Configure Migration Setttings:

  • Provide on-premises Exchange credentials

  • Microsoft 365 auto-discovers settings

4. Start the batch:

    • Choose “Automatically start” and “Automatically complete” options (recommended for cutover)

5. Wait for synchronization to complete:

    • Migration status can be monitored from the EAC

    • Expect it to take several hours, depending on mailbox size/count

6. Update DNS Records:

    • Once the batch completes, update your MX, Autodiscover, and SPF records to point to Microsoft 365

7. Assign licenses to each user (if not done earlier)

8. Reconfigure Outlook clients:

    • After DNS propagation, Outlook will auto-configure to Microsoft 365

Office 365 Cutover Migration PowerShell Steps

1. Connect to Exchange Online & Create Migration Endpoint:
				
					$onPremCred = Get-Credential
New-MigrationEndpoint -Name "CutoverEndpoint" -ExchangeRemoteMove -RemoteServer mail.domain.com -Credentials $onPremCred

				
			
2. Start the Batch:
				
					New-MigrationBatch -Name "CutoverBatch" -SourceEndpoint "CutoverEndpoint" -AutoStart -AutoComplete

				
			

B) Staged Migration

Best for: 150–2,000 users
Supported Exchange: 2003, 2007
Requires: Azure AD Connect, CSV of users, staged batches

Office 365 Staged Migration
Office 365 Staged Migration Flow

Staged migration moves mailboxes from Exchange 2003 or 2007 to Microsoft 365 in multiple batches over time. It’s ideal for organizations that want to move in phases, not all at once (like in a cutover 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.

Staged Migration Prerequisites

  • Verify your domain in Microsoft 365

  • Prepare your on-prem Exchange environment:

    • Set mailbox UPNs to match the user’s primary email address

    • Assign FullAccess to the admin account

  • Configure Azure AD Connect and synchronize users to Microsoft 365

  • Assign Microsoft 365 licenses to synced users

  • Ensure mail-enabled users exist in Microsoft 365 before migration

1. Prepare Migration CSV

First step is to prepare a CSV file containing users details.  The CSV file for a staged migration supports the following three attributes. Each row in the CSV file corresponds to a mailbox and must contain a value for each of these attributes.

AttributeDescriptionRequired?
EmailAddressSpecifies the primary SMTP email address, for example, pilarp@contoso.com, for on-premises mailboxes.
Use the primary SMTP address for on-premises mailboxes and not user IDs from the Microsoft 365 or Office 365. For example, if the on-premises domain is named contoso.com but the Microsoft 365 or Office 365 email domain is named service.contoso.com, you would use the contoso.com domain name for email addresses in the CSV file.
Required
PasswordThe password to be set for the new Microsoft 365 or Office 365 mailbox. Any password restrictions that are applied to your Microsoft 365 or Office 365 organization also apply to the passwords included in the CSV file.Optional
ForceChangePasswordSpecifies whether a user must change the password the first time they sign in to their new Microsoft 365 or Office 365 mailbox. Use True or False for the value of this parameter. If you implemented a single sign-on solution by deploying Active Directory Federation Services (AD FS) 2.0 (AD FS 2.0) or greater in your on-premises organization, you must use False for the value of the ForceChangePassword attribute.Optional

Here’s an example of the format for the CSV file. In this example, three on-premises mailboxes are migrated to Microsoft 365 or Office 365.

The first row, or header row, of the CSV file lists the names of the attributes, or fields, specified in the rows that follow. Each attribute name is separated by a comma.

				
					EmailAddress,Password,ForceChangePassword
mikep@infrasos.com,Pa$$w0rd,False
terryn@infrasos.com,Pa$$w0rd,False
sallyt@infrasos.com,Pa$$w0rd,False
				
			

Exchange Admin Center Migration Steps

  1. In the new Exchange Admin center, navigate to Migration > Batch.

  2. Select New Migration batch and follow the instructions in the details pane.

  3. In Migration Onboarding section, enter the batch name, select the mailbox migration path and select Next.

  4. Select the migration type as Staged migration from the drop-down list and select Next.

5. In Prerequisites section, read the following and select Next.

6. In Set endpoint section, you can either create a new migration endpoint or select the migration endpoint from the drop-down list: a. Select Create a new migration endpoint and follow the instructions to create the endpoints. b. Select the migration endpoint from the drop-down list and select Next.

7. Select and upload a CSV file containing the set of all of the users you want to migrate. The allowed headers are:

  • EmailAddress (required). Contains the primary email address for an existing Microsoft 365 or Office 365 mailbox.

  • Username (optional). Contains the Gmail primary email address, if it differs from EmailAddress.

8. In Add user mailboxes section, import the CSV file and select Next.

9. In Move configuration section, enter the details and select Next.

10. In Schedule batch migration section, verify all the details, select Save, and then select Done.

The batch status changes from Syncing to Synced, you can complete the batch.

11. To complete the batch, select the migration group.

12 In the details pane, select the preferred option to complete the batch and select Save.

The batch status is then Completed.

PowerShell Steps (Optional)

  1. Connect to Exchange Online and create a migration endpoint:
				
					$onPremCred = Get-Credential
New-MigrationEndpoint -Name "StagedEndpoint" -ExchangeRemoteMove -RemoteServer mail.yourdomain.com -Credentials $onPremCred

				
			

2. Create and start the batch:

				
					New-MigrationBatch -Name "StagedBatch01" `
  -CSVData ([System.IO.File]::ReadAllBytes("C:\StagedUsers.csv")) `
  -SourceEndpoint "StagedEndpoint" `
  -AutoStart:$true `
  -AutoComplete:$false

				
			

3. Manually complete after verifying success:

				
					Complete-MigrationBatch -Identity "StagedBatch01"

				
			

Post-Batch Actions

  • Assign Microsoft 365 licenses to newly synced users

  • Update MX records to point to Microsoft 365

  • Reconfigure Outlook profiles

  • Remove batch if complete:

				
					Remove-MigrationBatch -Identity "StagedBatch01"

				
			

C) Hybrid Migration

Hybrid migration enables full coexistence between on-premises Exchange and Microsoft 365. It allows mailboxes to be moved in small batches, while maintaining a shared GAL (Global Address List), calendar free/busy info, and centralized mail flow.

Best Use Case

ScenarioSupported
Long-term coexistence
Gradual mailbox moves
>2,000 users
Exchange 2010/2013/2016/2019
Exchange 2007 or earlier

Prerequisites

  1. Exchange Server: Exchange 2010 SP3 or later

  2. Azure AD Connect: Configured for directory sync

  3. Hybrid License: You can request a free Exchange Hybrid license

  4. Publicly trusted SSL certificate (e.g. for mail.domain.com)

  5. Public Autodiscover and EWS URLs must resolve externally

  6. Admin credentials for both Microsoft 365 and Exchange

Key Components

  • Hybrid Configuration Wizard (HCW): A tool that configures all connectivity

  • OAuth Authentication: Required for secure cloud <-> on-prem comms

  • Migration Endpoint: Used to create move requests

  • Mail Flow Connector: Optional for centralized routing

GUI Steps (Official Hybrid Migration)

1. Run Hybrid Configuration Wizard

👉 Download here: https://techcommunity.microsoft.com/blog/exchange/updated-hybrid-configuration-wizard-available/3859905

  • Run HCW on Exchange 2016/2019 server (or dedicated hybrid server)

  • Sign in to both your on-prem Exchange and Microsoft 365 tenant

  • Choose the type of hybrid:

    • Minimal Hybrid (good for short-term moves only)

    • Full Hybrid (recommended for full coexistence)

2. Validate HCW Completion

It configures:

  • Mail flow connectors (inbound & outbound)

  • Federation trust and organization relationship

  • Autodiscover redirection

  • Migration endpoint in Microsoft 365

PowerShell Steps (Mailbox Migration Only)

Once HCW is completed, you can move mailboxes using Exchange Online PowerShell:

				
					# Connect to Exchange Online
Connect-ExchangeOnline

# Initiate a move request for a user
New-MoveRequest -Identity user@domain.com

				
			

To view status:

				
					Get-MoveRequest | Get-MoveRequestStatistics

				
			

To remove completed requests:

				
					Get-MoveRequest | Remove-MoveRequest

				
			

Mail Flow Options in Hybrid

OptionDescription
Centralized Mail TransportMail flows from Exchange Online → on-prem for outbound
Decentralized Mail FlowMail is delivered directly from Microsoft 365

Choose during HCW setup. Most organizations do NOT need centralized mail flow unless specific compliance policies require it.

Gotchas & Best Practices

ConcernBest Practice
CertificatesMust match public DNS name (mail.domain.com)
LicensingAssign Microsoft 365 Exchange Online license before mailbox move
DNSLeave Autodiscover pointing to on-prem until final cutover
OutlookAutoconfigures automatically post-migration

Hybrid Office 365 Migration Checklist

  • Domain Verified in Microsoft 365

  • Azure AD Connect Sync Working

  • SSL Certificate Installed

  • External EWS/Autodiscover Test Passed

  • HCW Completed Without Errors

  • Migration endpoint verified

  • Mail flow tested post-move

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Step 5: Post-Exchange to M365 Migration Tasks and Cleanup

After mailboxes have been successfully migrated to Microsoft 365 using Cutover, Staged, or Hybrid migration, your job isn’t quite finished. This step ensures smooth end-user experience, maintains security posture, and removes legacy configurations no longer needed.

Why This Step Matters

Neglecting post-migration tasks can lead to:

  • Mail flow issues due to DNS misconfiguration

  • Outlook connectivity problems

  • Confusion around legacy server roles

  • Security misalignment with compliance standards

Compliance Mapping

FrameworkControlDescription
CIS Microsoft 365 v1.53.5 – Secure DNS SettingsEnsure MX and Autodiscover records point to Microsoft 365
NIST 800-53 Rev 5SC-12 – Cryptographic Key EstablishmentApplies to TLS and secure mail flow verification
ISO/IEC 27001A.13.2.1 – Information transfer policies and proceduresEnsures secure transition and mail routing after migration

Tasks by Migration Type

TaskCutoverStagedHybrid
Assign Licenses✅ Before move✅ Before move✅ Before move
DNS Update (MX, SPF, Autodiscover)🕒 Final step
Remove Migration BatchN/A (manual move reqs)
Decommission On-Prem Servers✅ Optional✅ Optional❌ (keep at least 1 Exchange server)
Test Mail Flow
Remove Legacy Mailboxes

Step-by-Step Post-Migration Tasks

1. Complete and Remove Migration Batch

For Cutover & Staged migrations:

				
					# Complete batch if not auto-completed
Complete-MigrationBatch -Identity "CutoverBatch"

# Remove the completed batch
Remove-MigrationBatch -Identity "CutoverBatch"

				
			

For Hybrid:

				
					# Remove completed move requests
Get-MoveRequest | Remove-MoveRequest

				
			

2. Update DNS Records

Ensure all DNS entries now point to Microsoft 365:

RecordPoints To
MXdomain-com.mail.protection.outlook.com
SPFv=spf1 include:spf.protection.outlook.com -all
Autodiscoverautodiscover.outlook.com
CNAMEssip, lyncdiscover, msoid, etc.

Use this tool to verify: https://mxtoolbox.com/

3. Test Mail Flow & Outlook Autoconfig

Use the Microsoft Remote Connectivity Analyzer:
🔗 https://testconnectivity.microsoft.com

Verify:

  • External mail arrives to Microsoft 365 inbox

  • Internal Outlook clients auto-configure via Autodiscover

  • SPF, DKIM, and DMARC are functioning properly

4. Clean Up On-Prem Exchange (Optional)

Applies to Cutover and Staged migrations only.

If you’re fully decommissioning on-prem Exchange:

  1. Migrate any remaining Public Folders

  2. Remove mailboxes from local AD (after sync disabled)

  3. Uninstall Exchange:

				
					Setup.exe /Mode:Uninstall /IAcceptExchangeServerLicenseTerms

				
			

💡 For Hybrid, you must keep at least 1 Exchange server for managing recipients (or use 3rd party tools).

5. Monitor Microsoft 365 Post-Migration

Enable reporting for compliance & health:

				
					# Example: View mailbox sizes
Get-Mailbox | Get-MailboxStatistics | Sort TotalItemSize -Descending | Select DisplayName, TotalItemSize

# Example: Audit recent logins
Search-UnifiedAuditLog -StartDate (Get-Date).AddDays(-7) -EndDate (Get-Date) -Operations UserLoggedIn

				
			

Also use:

6. Communicate with Users

  • Notify users their migration is complete

  • Share updated instructions for:

    • Outlook setup (if profile reset is needed)

    • Mobile devices

    • Webmail URL: https://outlook.office365.com

Final Checkpoint

✅ Mail flow verified
✅ Outlook clients working
✅ DNS records updated
✅ Batches cleaned up
✅ Compliance audit trail preserved

FAQs About Migrating Exchange to Office 365

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. 

Migrate 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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Picture of 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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