Microsoft Office 365 Migrations

Guide, Benefits, and Risks

As businesses across the globe asked employees to relocate to home offices in 2020, one of the most common business software productivity suites, Microsoft Office 365 (renamed Microsoft 365 in 2020), simplified the process of allowing employees to securely access their applications from any device, anywhere. Now as a growing number of companies prepare to make homeworking a permanent arrangement beyond the pandemic, many more may be migrating to O365.

Whether you are migrating to 0365 from an on-prem environment, moving from a legacy 0365 tenant or consolidating because of company mergers and acquisitions, there is a lot to think about with many interdependent and moving parts. To help you, on this page we’ve put together the benefits of O365, the migration pitfalls you should avoid, and hints and tips that will help to take the risk (and headaches) out of your enterprise 0365 migration.

Benefits of an 0365 Migration

There are many benefits for companies who adopt Office 365 including:


As employees become ever more distributed, moving to O365 allows them to access their applications and data wherever they are and from any device. Data is also protected against disasters, which could wipe out on-prem equipment.


By moving to the cloud, you can reduce CAPEX as well as OPEX in terms of purchasing, maintaining, powering, and cooling on-prem equipment.

You could also potentially benefit from reduced licensing costs as the move to O365 could involve transitioning away from volume licensing agreements with Microsoft to the O365 cloud-licensed version of MS Office.


While many businesses are concerned about security when moving to the cloud, 0365 has key security features built-in, such as automatic encryption.


The process of adding users to the system is simplified with the purchase of licenses that cover multiple employees.


By adopting O365 you can free up the time of members of your IT infrastructure project team to focus on more strategic tasks.

Risks of O365 Migration

Before you begin any enterprise O365 migration you should be aware the pitfalls:

Breaking Access

Of course, you want everyone to have the same level of access to mailboxes or apps such as SharePoint or OneDrive that they had prior to the move. But it can be easy to create access issues if you don’t have all the information available:

  • You’ll need to migrate more mailboxes than users due to shared team and group mailboxes and calendars. You need to know what they are and who should have access to them ahead of the migration.
  • Many email accounts – not just your VIP team – will have delegates and sometimes more than one. You’ll need to map these into your migration plan to avoid severing any delegate relationships.
  • When migrating user data within SharePoint and OneDrive, shortcuts and links within and to documents can break (due to the location change), so you’ll need to make users aware of the possibility, and that links will need to be re-established post migration.
Making work for yourself further down the line

If you haven’t cleaned up your data – particularly around the Active Directory metadata – you are going to cause frustration and perhaps failure when it comes to preparing for the migration. There are a number of tools that can help to validate the environment, such as Microsoft IdFix.


As previously mentioned, you are going to see CAPEX and OPEX reductions as a result of reducing the amount of hardware you maintain and run, but, completed manually, O365 projects can take a lot of time and any errors can lead to project failure and more costs.

One additional point to note is that if you are utilizing the ‘Enterprise’ licensing on O365 – this will include the licensing of your locally installed Office suite of applications – so if you do retain your volume license agreement you could be paying twice!


The key to a successful O365 migration is planning.

You need to have a clear picture of your current environment, mapping all the interdependencies between users, calendars, mailboxes and all other files you are moving before you execute your program.

But, run manually, by the time you have collated and cleaned your data, changes to the business will mean your information is already out of date – which inevitably will lead to issues and errors further down the line.

Take the effort and time out of running a successful O365 migration. Schedule a Demo.

Tips for a Smooth O365 Migration

collate all the data

Get a clear picture of migration scope:

  • Understanding what you are migrating. Email only? SharePoint? File servers or other on-prem resources?
  • Defining which users and groups you are migrating.
  • Understanding what you are migrating from - on-prem exchange or from a legacy O365 environment or a hybrid mix.
  • Checking for and understanding legal and regulatory compliance requirements.

collate all your information

Aggregate your information into a single view

Pull in information from your Exchange environments, Active Directory domains, spreadsheets, human resources systems and more, including understanding the size, settings and permissions of each mailbox in existing Exchange, SharePoint, File server or O365 environments.

Map interdependencies

Map interdependencies

You’re going to need a clear picture of which user has access to which folder, calendar and mailbox, so you need to work out file links and file server permissions, mailbox sharing, access permissions, delegates and more. It’s going to be a long process, but you’ll need to find a way to map all of these interdependencies so that you can recreate in the new O365 environment and not break access.


Understand how the migration will impact logins to single sign on (SSO) and web applications

Have a complete set of data for each user’s login protocols for all their resources and use that data to update login protocols or set up new ones.

Correct data mismatches

Correct data mismatches:

Given that you are pulling data in from various sources, it’s likely there will be inconsistencies, gaps and errors that you need to clean up:

  • Talk to managers and users to fill the gaps or clean up issues.
  • Delete out of date or invalid accounts.

Leverage dependencies

Leverage dependencies to plan your migration:

Work out how you need to migrate and in what order, using your source data to create a rollout schedule:

  • Talk with managers to find out if there are any blackout dates when it would be too risky to conduct any migrations.
  • Using your dependency mapping, work out how to migrate your users and mailboxes in waves.

select implementation

Work out what you don’t want:

If there are any elements of migrating to O365 that you don’t want to implement – such as Teams or OneDrive – you need to plan for these by implementing Active Directory Group Policy controls and test these before your rollout.


Define communications and validation plans:

  • Decide how and when you will communicate the rollout to end users and managers, providing them with information about the migration and how they can get help if there are any issues.
  • Identify key users that you can work with during and post migration to validate success.

Readiness for migration

Identify readiness for migration:

Leverage your source data and keep adding to it as the project progresses to compile reports on readiness for migration, success and failure and compliance reports.

Common Exchange Migration Methods

The migration method you use will depend on your current environment. Your choices include:

Cutover Migration

This method can be used for any version of Exchange but is required if your on-prem Exchange is MS Exchange Server 2003. A cutover migration can be completed over a number of days. You can migrate a maximum 2,000 mailboxes to O365 using this method, but Microsoft recommends a limit of 150.

Staged Migration

You can migrate all your organization’s mailboxes to O365 using a staged migration, migrating batches of on-prem mailboxes over the course of a few weeks or months.

Hybrid Migration

This allows you to migrate to O365 while keeping an on-prem server and providing the seamless look and feel of a single Exchange organization between Exchange organizations on-prem and in O365. This can serve as an intermediate stage to moving over to 0365.

IMAP Migration

 This method allows for migration from non-exchange platforms such as from Gmail, and is generally done in the “cutover” style, mentioned above.

How ReadyWorks can help you deliver a successful O365 migration

Let’s face it, keeping track of data in spreadsheets is a risky business. Anything entered incorrectly or missed altogether can cause issues down the line. And if you want to keep your data current, you are going to have to spend a lot of time going back to your data sources to correct and update information.

ReadyWorks automates more than 50% of manual tasks by connecting to and orchestrating all your tools, systems and databases to:

  • Create a real-time single view of all your data, allowing you to prioritize sources and implement workflows to clean up inconsistencies and find missing data.
  • Offer you a clear view of:
    • Group mailboxes and calendars.
    • Delegate relationships and other interdependencies – also known as ‘user affinity’.
    • Mailboxes and other data on legal hold.
    • Logins and SSO mismatches
  • Help you understand mailbox, data and folder sizes and, as a result, the time you need to allow for migration.
  • Allow you to define migration waves that leverage all interdependencies in real-time to enhance success.
  • Leverage templates and implement workflows based on dates such as automated end-user communications.
  • Provide you with customized dashboards that allow you to create reports on completions and failures, compliance and more – and share links so that stakeholders can see progress in real time.

Customer Success


Leading space technology and intelligence company, Maxar, used ReadyWorks for its O365 deployment and post-merger IT consolidation. ReadyWorks provided a cohesive view of data across all organizations and systems and automatically identified and migrated mailbox delegates. See how ReadyWorks task automation reduced projection completion time by 25%. →


“ReadyWorks was critical to our O365 migration planning process. Having an accurate view of users and their delegates in one location saved us months of labor and significantly reduced our program costs.”