General info

Mailbox migration from one Office 365 tenant to another. Usually you will need this type of migration when a company merges or acquires another company or you would like to migrate to a different geographic region.

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Long description Office 365 Tenant-to-Tenant Cutover Email Migration (100-300 users)
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Occasionally, a customer needs a migration inside the Office 365 cloud platform. For example, if one company acquires another company and both are using Office 365, there may be many reasons to start merging.

Our objective is to provide planning, design and migration from one Office 365 tenant to another.

A migration project will be considered successful if mailbox data is migrated without loss of data within an agreed time frame and with minimal possible downtime.

Please note that your email domain(s) that we will transfer between tenants will be unavailable for some time (usually minutes), during which NDRs will be delivered to anyone trying to send an email to these domain(s). To minimize downtime and user inconvenience, we define and use the best methods for migration. We may even decide to use an MX Spooler service to eliminate the need for downtime entirely.

IT Partner is responsible to

  • Export resources (mailbox-enabled users, contacts, groups, etc.) from the source tenant.
  • Import resources to the destination tenant via AD Connect or CSV import.
  • Change resources UPN/primary SMTP addresses as required for migration purposes.
  • Do pre-staging migration (only emails and email folder older than 30 days).
  • Do final mailbox migration with calendars, contacts, rules and other data.
  • Change records in domain(s) zones to accommodate the migration needs.

Client is responsible to

  • Provide a dedicated point of contact responsible for working with IT Partner. Coordinate any outside vendor resources and schedules.
  • Configure all networking equipment such as load balancers, routers, firewalls, and switches.
  • If Microsoft Outlook or other desktop email clients are to be used for connectivity to Office 365, deploy email software to 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 mailboxes 50 GB or larger and/or deleted folders 30 GB or larger).

Out of the scope of this project (additional cost items)

  • Informing users about upcoming changes
  • Training of customer team (could be added as additional service)
  • Migration of Corporate documents to SharePoint Online (could be added as additional service).
  • Desktop software settings

Upon completion of the engagement, we will provide a Project Closeout Report. This document will indicate final project status including evidence of meeting acceptance criteria, outstanding issues and final budget. If you want more extensive documentation – this can be provided for an additional fee.


  • You must have global-admin level access to the source Office 365 tenant.
  • You must have global-admin level access to the destination Office 365 tenant with Exchange Online licenses available.
  • You must have access to your email domain DNS zone.


May vary depending on your needs. 1. Kickoff meeting. 2. Pre-migration source system health check. 3. Creating users or configuring AD connect tool. 4. Start email migration. 5. Verify email migration. 6. Change MX record to new Office 365 tenant. 7. Final email migration. 8. Post-migration tasks.


  • Users can access Exchange Online from their desktop PC’s, mobile phones and tablets from any place, any time
  • Old Office 365 tenant successfully migrated to new tenant Office 365 and accessible by all users
  • All necessary Transport rules created and working
  • Mail flows flawlessly to and from Exchange Online
  • Exchange Online Protection is configured and working


Manufacturer IT Partner
Licensing SRV
Duration 14 days
Project Management Fee $25.00
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$ 25.00 per user
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