Mark Brezicky / / Categories: Office 365, Cloud, Microsoft 365

Office 365 Consolidation Lessons Learned Part 2

The first article in this series discussed the fundamental stages of a tenant to tenant migration.  Now that you understand the overall picture, this article will discuss the non-technical challenges with a tenant to tenant migration, while part 3 will cover the technical challenges.  From our experience, these non-technical factors play a significant role in the success of a consolidation:

  • People/process, communications, scheduling
  • Planning and preparation
  • Cost, budget, licenses
  • Order of operations: which workloads go first
  • Coexistence period
  • Multiple vendors/partners


People/process, communications, scheduling

This category has been by far the most challenging aspect for tenant to tenant migrations.  A small tenant consolidation two organizations simply involving Exchange Online is not complicated to coordinate.  However, the complexity increases exponentially in large organizations and multiple workloads within Office 365. 

During the initial stages of the migration, all stakeholders should be clearly identified.  That not only includes management and technical resources, but pilot groups and change management teams.

A plan should be developed to inform users of all phases of the consolidation/migration.  Even though they are moving laterally to the same platform, change management is as important for tenant to tenant migrations as it was in the initial migration to the cloud.  Don’t let your project be postponed at the last minute due to end users simply not having enough awareness of the changes that are occurring.

Enterprise-scale tenant-to-tenant migrations tend to require a Vegas-caliber Cirque du Soleil routine when it comes to scheduling all tasks to fit and execute as seamlessly as possible.  Any issues or delays due to non-technical logistics can impact the budget and/or timelines significantly. 

Planning and Preparation

Plan, plan, and plan some more.  Enabling cannot stress enough the proper attention and diligence that needs to be put into planning.  This goes for any project, big or small.  Planning for tenant to tenant migrations should not just be about technical planning, but also non-technical and logistical factors involved. 

Organizations and their IT partners/vendors should anticipate all non-technical factors including costs, timelines, schedules.  All stakeholders involved in the project should be accountable in their specific area to properly discover, plan, and prepare.  However, when it comes to logistics and coordination of executing the plan, all stakeholders need to collaborate together and lay out the requirements for each area to determine dependencies and business and technical requirements.

The current state and usage of workloads involved in the migration should be properly discovered and documented.  Then a desired end state diagram showing all workloads should be created.  This will greatly assist in creating an execution plan to go from the current state to the desired end state.  This in turn can be used for all budgeting and scheduling. 

Cost, Budget and Licenses

Once the proper planning has been completed, you should know exactly what the desired end state needs to be.  That should allow you to determine what to budget for based on the complexities of the migration.  However, always create some wiggle room in the budget for the unexpected situations.

Cost associated with a tenant to tenant migration have some typical anticipated expenses with any project, but also can include some unique items as well.  Several costs to anticipate include:

  • 3rd party tools required
  • Microsoft 365 licenses
  • Professional Services from partner
  • 3rd party service integrations
  • Other value-added services
  • Other indirect costs (i.e. lost revenue due to downtime, data loss)                            

The last bullet point mentioned above is a huge unknown variable.  With proper planning and execution, no indirect costs will be incurred.  However, if you encounter a situation such as downtime or data loss, you may find yourself with significant lost revenue due to missing customer and sales emails or even large fines due to data loss on legal matters.

Licenses are another specific topic to consider in your upfront planning.  Here are a few questions to ask yourself, your partner, or even your Microsoft rep when discussing licenses for tenant to tenant consolidations:

  • Can licenses be transferred to the new tenant?
  • How much time is left on current agreement for the source tenant?
  • Do you have enough licenses to cover all combined users in the target tenant?
  • Do I need any additional licenses to provide certain features to newly acquired users (i.e. MFA, ATP, etc.)?
  • What will the post-migration licensing cost be?
  • Will I be billed double for licenses? If so, for how long? 

Order of operations: which workloads go first

Office 365 has several core workloads, including Exchange Online, SharePoint Online\OneDrive for Business, and Skype for Business Online\Microsoft Teams.  There is no universal order for which workload to move first.  This primarily depends on the current state of each application, business and technical requirements, as well as utilization.  Ultimately, this should be a dedicated topic when planning and coordinating the migration.  You may be able to break workloads up and do them one at a time, but you may find a certain technical or non-technical challenges that requires all workloads be migrated at the same time.  As shown in the previous article, here are the pros and cons of each migration type.


Coexistence period

A cutover is typically the best approach for all types of tenant to tenant migrations regardless of workload.  If you are able to plan and prepare for a cutover, it is possible to do so in a single weekend, even for tenants with thousands of users.

However, if the business requires to have coexistence for an extended period of time or to do batch migrations, it is possible.  There are significant complexities involved that are unique to each workload to achieve long term coexistence, unless usernames and email addresses are able to change (which is rarely the case).  For example, if there is a need to maintain a shared email address space across two tenants, Microsoft offers an initial domain using where you can forward emails to.  That combined with an Address Rewrite setup (3rd Party SMTP gateway like Proofpoint or on-premises Exchange Edge Servers) will allow you to manipulate mail flow to the point where all users appear to be sending from a single email address space across two tenants. 

Again, the cutover method is preferred, but if the business requirement demands coexistence, then the appropriate workload planning and testing needs to be accounted for when preparing for coexistence. 

Multiple Vendors/Partners

Finally, when dealing with Office 365 you have many core services such as Exchange Online, SharePoint, Skype for Business/Teams.  You may find yourself working with multiple vendors and partners to accomplish a massive deployment and cutover.  This adds to the complexities of coordination and schedules.  Even if you are fortunate to find a partner with expertise in all areas to be migrated, there are still most likely to be several engineers involved from both customer and partner side. 

In the next part of this series, we will dive deeper into technical challenges of any tenant to tenant migration that you should anticipate.  Enabling Technologies can help you enable secure productivity in the cloud by properly preparing you for moving to Azure AD and Office 365 based on Microsoft Best Practices.  You can check out more in the Cloud section of our website. 


Work with our team of Cloud Computing Consultants who have done this so many times they know all of the “minefields” to prevent missteps.

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