Preparation, Preparation, and More Preparation

Migrations in Microsoft 365 are a complex beast. It seems every time you feel like you have captured everything, more apps or functionalities appear. Every shiny new tool Microsoft releases is another consideration for migration teams and IT departments.

Planning for migrations – tenant-to-tenant or otherwise – is a mammoth task and there are many variables to consider. It’s very easy to feel like something has been left behind, even if you’re not quite sure what that something is!

There are tools to help with planning (such as this tenant-to-tenant Migration Assessment Script) and numerous migration tools, native or otherwise, available to facilitate the actual migration process. The problem is each of these tools requires you to know everything you need to migrate. In my experience, this is rarely the case.

Where to Start?

The starting point for many organizations is the “heavy hitters” of Microsoft 365: Exchange Online, SharePoint, OneDrive, and Teams. These are the most visible apps that users access and much of the reporting available in the tenant is centered around these workloads. Crucially, they also host most of the business data in the tenant, often underpinning other services.

Another key aspect is identity. Understanding how user identities will be brought to the new environment is critical to any migration and arguably has the largest impact on the end-user experience. This can be as simple as setting up new identities in the target, or as complex as performing a full Active Directory migration to retain user access and credentials.

What Else Do We Need to Consider?

Outside of the items listed above, there is a myriad of other items that need to be considered. For example, I mentioned how identity is a key consideration for Microsoft 365, but so are any external applications that leverage Azure AD as an authentication provider. Many organizations provide single sign-on to SaaS applications through Azure AD. In this scenario, migrating from the current Azure AD tenant will effectively break access to a key line of business applications.

Another example is end-user local files. Often in a tenant-to-tenant migration scenario, we aren’t just moving users to a new tenant, but potentially their devices as well. This is becoming increasingly common as the case for Azure AD joining devices becomes more attractive for organizations. I’ve seen organizations use Windows Autopilot to allow end-users to migrate their own devices remotely to a new tenant in a few easy steps. What isn’t always considered here are files on the device.

For instance, it would be great if all user files were in their OneDrive folder and synced to the cloud with no errors, but realistically, expecting that this is the case in the real world is quite naive. The OneDrive Sync Client has definitely improved in recent years and errors are less frequent, but they do still happen. The addition of the OneDrive Sync Health Dashboard to the Microsoft 365 Apps admin center provides some much-needed visibility into the performance of the OneDrive Sync Client, but it is still a preview feature currently.

Also not covered by OneDrive are any files that users have been stored outside of their OneDrive known folders – like that certificate that sits on a user’s C: drive which allows them to access banking services for the organization, or the years’ worth of PST files that a user has created as an archive.

Also easily missed are Power Platform components, particularly those built by “Citizen Developers”. It’s not uncommon for organizations to have apps or flows that run critical business processes which the IT department is not fully aware of. A simple flow to download and process attachments from an email message could cause major issues if it is not present on day 1 in the new environment.

How to Approach Discovery

These are just some of the many moving parts in a migration project that need to be captured, and the list continues to grow. Given the complexity involved, it’s important that the discovery process is given the appropriate time and energy to identify as many of the unknowns as possible. Something that techies like me don’t always consider is that discovery is not purely a technical exercise, it should also include business engagement and understanding.

Running technical assessments is a great starting point to gather those key workloads, but I also strongly recommend talking to each department and understanding what is important to them and how they work. Explaining to end-users what the plan is and working with them to understand how it may impact them is invaluable and can highlight some vital business practices to consider.

For migration to be successful, the entire business must be taken along on the journey. Including stakeholders from key business sectors will allow information to flow both ways and reduce the burden on technical teams.

Communication is Key

Technical considerations aside, a robust adoption and change management program can be the difference between a technically successful project being seen as a success or a failure to the wider business. If all the technical aspects of a project are delivered on time and on budget, but the end-user experience was poor, the project will not be a success.

The first day after a user is migrated can be a confusing time – even for tech-savvy users. Small things that don’t seem like a big deal to the migration team like SharePoint site URLs, migrated Teams meetings, or new naming conventions can often prevent users from getting their work done. If people can’t get their work done, they tend to get annoyed, and this overshadows the amount of work that has gone into making the migration happen in the first place.

A good change management program can ensure that users understand what is going to happen and that they are equipped with all the information they need to stay productive during the change. This should also be supported by a clear user acceptance testing (UAT) plan to validate the environment prior to bringing users across.

What Else Are We forgetting?

In this article, I’ve listed just a few of the many components that need attention during migrations. As with any task as complex as this, it should be approached in a step-by-step manner. The planning and discovery phase should not be understated and it quite often represents most of the effort in a migration.

To learn more about commonly overlooked aspects of migrations, check out this webinar on September 8th: You’ve migrated… But what did you leave behind?

You’ve migrated… But what did you leave behind?

To learn more about commonly overlooked aspects of migrations, check out our on-demand webinar!

About the Author

Sean McAvinue

Sean McAvinue is a Microsoft MVP in Office Development and has been working with Microsoft Technologies for more than 10 years. As Modern Workplace Practice Lead at Ergo Group, he helps customers with planning, deploying and maximizing the many benefits of Microsoft 365 with a focus on security and automation. With a passion for creative problem solving, he enjoys developing solutions for business requirements by leveraging new technologies or by extending the built-in functionality with automation. Blogs frequently at and loves sharing and collaborating with the community. To reach out to Sean, you can find him on Twitter at @sean_mcavinue


  1. Michael Mahady

    Thanks Sean, interesting article.
    Hope you’re keeping well.

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