Cutover Exchange Online Migration — Move On-Premises Exchange to Microsoft 365
This service migrates mailboxes from a customer-hosted and customer-managed on-premises Exchange Server to Exchange Online in Microsoft 365 using a cutover approach, with all mailboxes migrated at once. It is for customers running at least one Exchange Server on-premises who need IT Partner to plan, execute, monitor, and complete the mailbox migration to Exchange Online.
What this engagement is
IT Partner helps migrate Exchange mailboxes from your on-premises Exchange Server to Microsoft 365 Exchange Online. The engagement includes planning the cutover, preparing Exchange Online mailboxes, validating email domains, starting and monitoring the migration batch, setting up incremental mailbox synchronization, resolving migration issues, changing DNS settings, and closing out the project after migration completion.
Success criteria
What you receive
How the work unfolds
Exchange contact information, confirm the migration scope and mailbox count, agree the schedule and cutover window, and plan key steps with your team.
Review the source Exchange Server for migration readiness, including connectivity, certificates, mailbox list and sizes, and any conditions that could affect migration throughput.
Create Microsoft 365 user accounts or configure Microsoft Entra Connect synchronization for existing Active Directory users, and assign Exchange Online licenses.
Add and validate the email domain(s) in Microsoft 365, confirm access to the source system, and prepare the migration batch settings.
Start the cutover migration batch and begin the initial synchronization of mailboxes to Exchange Online.
Monitor migration progress, review the migration report, and resolve mailbox-level errors so all mailboxes migrate successfully.
During the agreed cutover window, change the MX record and related DNS records so inbound mail is delivered to Exchange Online.
Run incremental synchronization to capture email received during the transition, then complete the final migration pass.
Verify mail flow and user access, stop incremental sync, delete the migration batch, and prepare the project closeout report.
Prerequisites
Who does what
IT Partner
- Hold a kickoff meeting to exchange contact information, plan key steps, and discuss the project
- Provide new Exchange Online mailboxes by creating Microsoft 365 user accounts and assigning Exchange Online user licenses
- Add and validate email domain(s) to Microsoft 365
- Start a migration batch
- Provide a report with the number of mailboxes that were successfully migrated and those that cannot be migrated, if any
- Incremental mailbox synchronization setup to receive any emails sent after the start of the main synchronization
- Resolve any migration issues and errors to ensure that all mailboxes have been successfully migrated
- Plan and guide the cutover from the source system to Exchange Online
- Change DNS settings and control their application
- Monitor health and status of the destination Exchange Online environment to make sure the migration process is correct
- Delete the migration batch after the migration is completed and incremental sync is stopped
Your team
- Provide a dedicated point of contact responsible for working with IT Partner and coordinate any outside vendor resources and schedules
- Configure all network equipment, such as load balancers, routers, firewalls, and switches
- Provide access to physical and virtual servers and/or systems and services as needed. Provide remote and/or physical access to facility and systems required to complete the work
- Perform changes to internal and external DNS, as required
- Assist with identification of high-risk users (top executives and VIP users, users with 50 GB mailboxes or larger and/or 30 GB deleted folders or larger)
- Review and approve engagement deliverables in a timely manner
What's not included
Limitations & technical notes
Frequently asked questions
What is the Cutover Exchange Online Migration service?
This service migrates mailboxes from a customer-hosted, customer-managed on-premises Exchange Server to Exchange Online in Microsoft 365 using a cutover approach. In a cutover migration, all mailboxes are migrated at once, and IT Partner plans, executes, monitors, and completes the migration process.
Who is this Exchange Online migration service for?
This service is for organizations that currently run at least one on-premises Exchange Server and want to move their mailboxes to Exchange Online in Microsoft 365. It is specifically designed for a cutover migration, so it is best suited when the business is ready to migrate all mailboxes together rather than in staged waves.
What is included in the Exchange cutover migration service?
The service includes migration planning, Exchange Online mailbox preparation, Microsoft 365 domain validation, migration batch creation, incremental mailbox synchronization, DNS cutover guidance and changes, monitoring, issue resolution, and project closeout reporting. IT Partner also verifies the destination Exchange Online environment health and provides a report showing which mailboxes migrated successfully and whether any could not be migrated.
What is not included in this migration service?
This service does not include customer team training, desktop software settings, end user support, or extensive documentation beyond the project closeout report. Those items may be available as additional services, but they are outside the stated scope of this migration engagement.
How long does the cutover Exchange Online migration take?
The listed service duration is 1 week. The actual schedule depends on the customer environment, readiness, DNS access, mailbox sizes, source system health, and how quickly required approvals and access are provided.
How is the service priced?
This migration is currently listed as Free (Microsoft Sponsored). Confirm eligibility for the Microsoft-sponsored offer and the final scope with IT Partner before the engagement begins — any work outside the stated scope is quoted in writing before work begins — you pay after you approve delivery.
What prerequisites must be in place before the migration starts?
You must have a Microsoft 365 tenant with Exchange Online licenses, access to your email domain DNS zone, and a full installation of Exchange Server in your environment. The Exchange Server must also have a valid UCC SSL certificate, and the service notes that the Exchange Server can be licensed for free with the appropriate Microsoft 365 plan.
What happens during the migration engagement?
The engagement typically starts with a kickoff meeting and a pre-migration source system health check, followed by user creation or Microsoft Entra Connect configuration, migration preparation, migration batch start, migration verification, MX record cutover, final migration, and post-migration tasks. IT Partner monitors the Exchange Online destination environment and migration progress throughout the process to help ensure the migration is proceeding correctly.
Will all mailboxes be migrated at the same time?
Yes, this is a cutover Exchange migration service, so all mailboxes are migrated at once. If your organization needs a staged, phased, or hybrid migration approach, you should confirm a different migration scope with IT Partner.
How is mail flow handled during the cutover?
IT Partner sets up incremental mailbox synchronization to capture email sent after the main synchronization begins, then plans and guides the cutover from the source Exchange system to Exchange Online. The service also includes changing DNS settings, including the MX record to the new Microsoft 365 tenant, and controlling their application so mail can be sent and received through Exchange Online after cutover.
Is downtime expected during the migration?
Cutover migrations involve a DNS/MX change and all mailboxes moving at once, so plan for a short mail-flow transition window. IT Partner sets up incremental synchronization to capture email sent during the transition and coordinates the cutover timing with you to minimize business impact.
What is the customer responsible for during the migration?
The customer must provide a dedicated point of contact, coordinate outside vendors, configure network equipment such as firewalls and routers, provide access to required servers and systems, perform or assist with internal and external DNS changes as required, identify high-risk users, and review deliverables promptly. These responsibilities are important because delays in access, DNS, networking, or approvals can affect the migration schedule.