Microsoft 365 Tenant-to-Tenant Cutover Email Migration — Exchange Online Mailbox Move
IT Partner provides planning, design, and migration of email service from one Microsoft 365 tenant to another. This service is usually needed when a company merges with or acquires another company, when both organizations use Microsoft 365, or when an organization wants to migrate to a different geographic region.
What this engagement is
Occasionally, a customer needs a migration inside the Microsoft 365 cloud platform. For example, if one company acquires another company and both are using Microsoft 365, there may be many reasons to start merging. This service provides planning, design, and migration of email service from one Microsoft 365 tenant to another. While the domain is transferring from the source tenant to the new tenant, incoming mail will not be received for about 24 hours because of domain name binding features in Exchange Online. To avoid loss of emails during the transfer period, you can consider the extended migration service.
Success criteria
What you receive
How the work unfolds
Confirm business objectives, migration scope, source and destination tenant details, key contacts, mailbox count, high-risk users, cutover window, communication approach, and decision-making process for the tenant-to-tenant cutover.
Review the source tenant and destination tenant readiness, including domains, accepted domains, mail flow, mailbox sizes, licensing, Exchange Online configuration, DNS access, transport rules, and known risks that could affect the migration.
Prepare destination identities and mail objects by creating or synchronizing users, assigning required Exchange Online licenses, importing contacts and groups as applicable, and validating that target mailboxes or mail-enabled objects are ready for migration.
Configure the migration approach and begin the pre-stage migration for eligible mailbox content, focusing on emails and email folders older than 30 days, while monitoring migration progress and addressing initial errors.
Validate pre-stage migration results by checking selected mailboxes, folder structure, item counts where available, migration reports, and any failed or skipped items that require remediation before cutover.
Coordinate the cutover window and update required public DNS records, including the MX record and related mail flow records as required, so inbound mail is directed to Exchange Online in the destination tenant.
Perform the final migration pass to move recent mailbox data and remaining mailbox content, including calendars, contacts, rules, and other in-scope mailbox data, then confirm completion status for migrated users.
Validate user access, inbound and outbound mail flow, Exchange Online Protection, and required transport rules in the destination tenant; assist with migration-related issue review; and prepare the project closeout report.
Prerequisites
Who does what
IT Partner
- Export resources (mailbox-enabled users, contacts, groups, etc.) from the source tenant
- Import resources to the destination tenant via AD Connect or CSV import
- Do pre-stage migration (only emails and email folders older than 30 days)
- Final mailbox migration with calendars, contacts, rules, and other data
- Change records in domain zones to accommodate migration needs
Your team
- Provide a dedicated point of contact responsible for working with IT Partner
- Coordinate any outside vendor resources and schedules
- Configure all network equipment, such as load balancers, routers, firewalls, and switches
- If Microsoft Outlook or other desktop email clients are used to connect to Microsoft 365, deploy email software on client workstations
- 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)
- Recreate new Outlook profile on all client workstations, if desktop Outlook version is used
- Inform users about upcoming changes and provide the necessary information
What's not included
Limitations & technical notes
Frequently asked questions
What is the Microsoft 365 tenant-to-tenant cutover email migration service?
IT Partner’s Microsoft 365 tenant-to-tenant cutover email migration service plans, designs, and migrates email service from one Microsoft 365 tenant to another. It is commonly used after mergers and acquisitions, when both organizations already use Microsoft 365, or when a company needs to move email to a tenant in a different geographic region.
What is included in IT Partner’s tenant-to-tenant email migration service?
The service includes exporting mailbox-enabled users, contacts, groups, and related resources from the source tenant, then importing them into the destination tenant by AD Connect or CSV import. It also includes pre-stage migration of emails and email folders older than 30 days, final mailbox migration of calendars, contacts, rules, and other mailbox data, required domain zone record changes for the migration, and a project closeout report.
What is not included in the tenant-to-tenant email migration service?
The service does not include informing users about upcoming changes, customer team training, migration of corporate documents to SharePoint Online, or desktop software settings. More extensive documentation than the project closeout report, customer training, and SharePoint Online document migration can be provided only as additional services if agreed with IT Partner.
What Microsoft 365 workloads are migrated by this service?
This service is focused on Exchange Online email migration between Microsoft 365 tenants. It covers mailbox content such as email, email folders, calendars, contacts, rules, and other mailbox data, but it does not include corporate document migration to SharePoint Online.
What prerequisites are required before a tenant-to-tenant email migration can start?
Before the migration starts, global admin level access is required to both the source Microsoft 365 tenant and the destination Microsoft 365 tenant. The destination tenant must have available Exchange Online licenses, and access to the email domain DNS zone is also required because domain and mail flow records must be changed during the migration.
What happens during the tenant-to-tenant email migration project?
The project typically includes a kickoff meeting, a source system health check, user creation or AD Connect configuration, email migration start, migration verification, MX record change to the new Microsoft 365 tenant, final email migration, and post-migration tasks. The exact plan may vary depending on customer needs and the state of the source and destination tenants.
Will there be email downtime during the Microsoft 365 tenant-to-tenant cutover?
Yes, incoming mail will not be received for about 24 hours while the domain transfers from the source tenant to the destination tenant. This is due to domain name binding behavior in Exchange Online, so customers should plan for a mail flow impact during the cutover window.
Can email loss be avoided during the domain transfer period?
The standard cutover service notes that incoming mail will not be received for about 24 hours while the domain transfers between tenants. To avoid loss of emails during that transfer period, you can consider the extended migration service.
When is the MX record changed during the migration?
The MX record is changed after initial migration work and verification steps are completed, as part of moving mail flow to the new Microsoft 365 tenant. This change is a critical cutover step because it directs new inbound email to Exchange Online in the destination tenant.
What mailbox data is migrated in the final migration?
The final mailbox migration includes calendars, contacts, rules, and other mailbox data in addition to email. Earlier in the project, IT Partner performs a pre-stage migration of only emails and email folders older than 30 days, which helps prepare mailboxes before the final cutover.
What does pre-stage migration mean in this service?
Pre-stage migration means IT Partner migrates emails and email folders older than 30 days before the final cutover. This reduces the amount of older mailbox content that must be handled during the final migration phase, although the exact business impact depends on the customer environment.
What are IT Partner’s responsibilities during the migration?
IT Partner is responsible for exporting resources from the source tenant, importing resources into the destination tenant using AD Connect or CSV import, performing the pre-stage and final mailbox migrations, and changing domain zone records needed for the migration. IT Partner also provides a project closeout report showing final project status, acceptance criteria matching, outstanding issues, and final budget.
What are the client’s responsibilities during the migration?
The client must provide a dedicated point of contact, coordinate outside vendors and schedules, configure network equipment if needed, deploy email software on client workstations if Microsoft Outlook or other desktop email clients are used, perform changes to internal and external DNS as required, and identify high-risk users such as executives, VIP users, or users with very large mailboxes. The client is also responsible for informing users about upcoming changes and recreating new Outlook profiles on client workstations if desktop Outlook is used.
Do users need new Outlook profiles after the migration?
Yes, if users connect with the desktop version of Microsoft Outlook, the client is responsible for recreating new Outlook profiles on all client workstations. Desktop software settings are outside the included migration scope.
How are high-risk users handled in a tenant-to-tenant email migration?
The client helps identify high-risk users before the migration, including top executives, VIP users, users with mailboxes of 50 GB or larger, and users with deleted folders of 30 GB or larger. Identifying these users early helps the migration team plan and validate those accounts carefully, although the service description does not specify a separate high-risk user migration track.
What are the success criteria for the migration?
The migration is considered successful when users can access Exchange Online from desktop PCs, mobile phones, and tablets; the old Microsoft 365 tenant email service has been migrated to the new tenant and is accessible; mail can be sent and received using Exchange Online; required transport rules are created and working; and Exchange Online Protection is configured and working.
Is Exchange Online Protection configured as part of the service?
Exchange Online Protection being configured and working is one of the stated success criteria for this migration service. The expected outcome is that Exchange Online Protection is configured and working in the destination Microsoft 365 environment.
How long does a Microsoft 365 tenant-to-tenant email migration take?
The listed service duration is 1 week. The migration plan may vary depending on customer needs, tenant readiness, mailbox sizes, DNS coordination, and migration complexity.
How is pricing determined for this tenant-to-tenant migration service?
The listed price for this service is $900 plus $25 per mailbox. Additional services, such as customer team training, SharePoint Online document migration, or more extensive documentation, may require additional fees if agreed with IT Partner.
What happens after the migration is completed?
After the migration, IT Partner performs post-migration tasks and provides a project closeout report. The report indicates final project status, whether acceptance criteria were met, any outstanding issues, and the final budget.