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Written By Harshita Sachdeva
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Approved By
Shivam Rathore -
Updated on October 8th, 2026
Migrate 250 Microsoft 365 Users to New Tenant: Secure Tenant-to-Tenant Migration for Enterprises
Fact-checked and reviewed in accordance with our
Editorial Policy
Migration Overview: Large firms and enterprises have a large number of employees. There is a Microsoft account associated with each one of these users, where they store emails, calendars, contacts, OneDrive files, Teams conversations, and much more. When these organisations undergo mergers, acquisitions, tenant consolidation, and look forward to restructuring the business, they perform cross-tenant migration. But specifically, for an enterprise-level migration project, the number of users might increase to 250 users or more. As a result, the migration process is not limited to creating accounts in another tenant. Thus, enterprises use the Aryson Tenant-to-Tenant Migration to migrate 250 Microsoft 365 users to new tenant quickly and reliably.
How Does Organisational Migration Differ From Standard One
A standard Microsoft 365 cross-tenant migration might involve a small number of users. Whereas, when it comes to organisational projects, this number might increase to 250 or more users. As the number of users increases, so does the complexity of migration because this migration would now involve accounts, mailboxes, identities, licences, permissions, and data. Thus, it becomes important to correctly coordinate, map, and validate both tenants accurately.
Key differences lie in scale – rather than the migration concept itself. When migrating on an enterprise level, dividing 250 users into carefully managed batches is essential – beginning with a test group to see how well it works out and fixing any problems that arise. Only after validating all your migrated information will you apply this method to subsequent groups safely.
What Data Needs to Be Migrated?
For 250 users, create an inventory of the workloads involved.
| Workloads | Data to Consider |
| Exchange Online | Emails, attachments, calendars, contacts, tasks & notes |
| SharePoint | Sites, libraries, documents, permissions |
| Teams | Chats, meetings, teams, channels, files |
| OneDrive | Files, folders, permissions, sharing |
| Groups | Membership, ownership, group resources |
| Identities | Users, UPNs, SMTP addresses, mappings |
Exactly How Much Data Do 250 Users Represent?
The number of users alone would not decide the complexity of the migration process. You can calculate the expected volume of data before you migrate 250 Microsoft 365 users to new tenant.
For instance, if each user has a 15 GB mailbox:
| 250 × 15 GB = 3.75 TB |
At the same time, if each user has 30 GB of OneDrive data to migrate,
| 250 × 30 GB = 7.5 TB |
Therefore, the combined data of Exchange Online and OneDrive would be considered and would approximately result in 11.25 TB of data.
*This is only an example. Actual mailbox and OneDrive sizes should be obtained from the source tenant.*
What to Check Before You Move 250 Office 365 Users to New Tenant?
There are certain parameters that one needs to consider before they proceed to the migration process. Make sure all the necessary steps in the Microsoft 365 cross-tenant migration checklist are fulfilled before you proceed further. A few of them are listed below.
1. Create a User Mapping
The first step is to prepare a source-destination (A-B) mapping like the ones below.
| Source | Destination |
| john@companyA.com | john@companyB.com |
| sara@companyA.com | sara@companyB.com |
During this process, recording every user’s UPN, SMTP address, mailbox size, OneDrive size, license information, group memberships, Teams memberships, and significant permissions becomes very critical indeed.
2. Check Licences
Review the licences available in both tenants. Microsoft’s current cross-tenant mailbox migration process requires the applicable Cross-Tenant User Data Migration licensing for users being migrated.
3. Review Domains
Identify the organisation’s custom domains and plan their movement carefully. Also review:
- MX
- SPF
- DKIM
- DMARC
- Autodiscover
- Mail connectors
A domain cannot simply be active in both tenants at the same time, so domain changes should be included in the cutover plan.
4. Review Permissions
Document your mailbox delegations, ‘send as’, ‘send on behalf’, calendar permissions, OneDrive shares, SharePoint permissions – and also who owns Teams before you start migrating.
How to Migrate 250 Microsoft 365 Users to New Tenant?
Either you manually migrate 250 users between tenants or use the professional tool’s CSV import feature to quickly migrate workload data in one go.
Native Method to Transfer 250 Microsoft 365 Users to New Tenant
Microsoft’s own Orchestrator tool allows users to move the supported M365 user data from one tenant to another. So it’s quite feasible for administrators to move over Exchange Online, OneDrive, Teams chats, and Teams meetings – all once they’ve completed their migration steps. These steps could very well involve tenant set-up, permissions, licensing, and mapping out users.
Best suited for: Enterprises’ IT teams that can efficiently administration & Powershell of Microsoft 365. However, for each workload, the requirements might vary, and there is a need for additional planning in case of Teams and SharePoint migration.
Simplified Steps to Migrate 250 Microsoft 365 Users to New Tenant
- Create destination users >> assign the required licences.
- Prepare the source (say A) and destination (say B) tenants for migration.
- Set up the migration apps, permissions, and settings.
- Make sure the supported workloads are prepared, like Exchange Online, OneDrive, and Teams.
- Map the source and destination identities and validate the pre-migration setup.
- Resolve the configuration problems, if any, and create batches for migration.
- Begin the migration and test on a pilot batch (taking a small amount of data first).
- Track the entire migration process & check if any item fails or gets skipped.
- Check whether the required data is migrated properly to the destination or not.
- At last, you can complete the cutover and move all users to the destination.
Microsoft 365 Migration Limits to Know
Some limits can directly affect the Microsoft 365 tenant to tenant migration for 250 users.
| OneDrive | Microsoft currently documents a 5 TB or 1 million-item limit for an individual OneDrive account in its cross-tenant migration guidance. |
| SharePoint | An individual SharePoint site has a documented 5 TB or 1 million-item limit for the cross-tenant migration scenario. |
| Exchange | Microsoft documents service-specific mailbox, message-size, and migration limitations for Exchange Online. Large messages, attachments, mailbox size, and service throttling can affect migration performance. |
| Teams | A team can have up to 25,000 members and 1,000 channels. A private chat can contain up to 250 people, while a chat message is approximately 100 KB |
Why Don’t Enterprises Prefer Native Methods
- Managing 250 user mappings requires significant administrative effort.
- Different workloads require separate migration processes and configurations.
- Large datasets require individual size and limit checks.
- Failed migrations require troubleshooting and repeated submissions.
- Managing multiple batches increases administrative coordination requirements.
- Tracking progress across workloads requires multiple administrative interfaces.
- Validating migrated data across 250 users takes time.
- Domain and mail-flow changes complicate final cutover.
- Teams data requires separate planning for supported workloads.
- Post-migration verification adds substantial administrative workload.
Professional Method to Migrate 250 Microsoft 365 Users to New Tenant
Migrating 250 users between tenants is a complicated task in itself. Also, it might consume a significant amount of time to accomplish. Aryson has come up with its Tenant-to-Tenant Migration Software. This software consists of a CSV import feature along with an admin mode to authenticate the source and destination accounts. The admin mode lets enterprises migrate data items from all sub-users in one go. Whereas the CSV import feature enables bulk migration capability & allows organisations to import a single CSV file containing multiple users. Whether it be 250 users or even more than that, this software makes sure to migrate data within a few clicks, that too, without losing data integrity.
Simplified Steps to Migrate 250 Microsoft 365 Users to New Tenant
- Download, set up, and execute Aryson’s Tenant-to-Tenant Migration Tool.
- Then select which workloads are essential for your migration needs.
- Connect to the source tenant via Modern Auth or client ID or secret.
- Select the required mailboxes, sites, OneDrive data, or Teams from the displayed ones.
- Log in to the destination tenant via Admin mode or load users with CSV import.
- Map source-to-destination user accounts and apply date or folder filters.
- Click Start Migration to begin the cross-tenant transfer.
- After migration, monitor the migration process via the progress bar.
However, the above steps will help you migrate data that too without investing much time; it is recommended to read the complete documentation of the software. This will eventually lead to a successful migration process.
Watch the Complete Migration Video
Troubleshooting Guide to Use During a 250-User Migration
There might occur multiple errors during the migration of 250 Microsoft 365 users between tenants. Therefore, the points below cover all the required steps one can take to resolve these errors.
| Problems | Troubleshooting |
| Incorrect user mapping | Verify source and destination UPNs before migration. |
| Domain conflicts | Remove source-tenant dependencies before destination verification. |
| Large mailboxes | Identify high-volume users and migrate them separately. |
| Missing permissions | Record delegation and sharing permissions before migration. |
| Microsoft 365 throttling | Monitor migration speed and adjust batch sizes |
| Outlook access issues | Reconfigure Outlook profiles for the destination tenant. |
Conclusion
When you migrate 250 Microsoft 365 users to new tenant, there’s so much more involved than just migrating. Before starting your migration process, planning data transfer is very important – both at the user level and for your workloads. Users may start by mapping 250 identities and then calculating the total Exchange, OneDrive, SharePoint, and Teams data. Then, proceed with the pilot migration via the manual approach or the professional method discussed above, and apply the suitable approach to the entire dataset. To minimise throttling and quickly migrate all 250 users, it is recommended to use the software’s CSV import feature to achieve a successful migration.
Frequently Asked Questions
Q.1 How do I migrate 250 Microsoft 365 users to a new tenant?
Ans: First, you must plan the migration process, perform all the pre-migration steps, and use either the manual method or the professional one to begin the process. However, both methods work well; it is highly recommended to use the software for quick and secure migration.
Q.2. What Microsoft 365 data can be migrated between two tenants?
Ans: When it comes to the software, it can migrate Exchange Online mailboxes, OneDrive, SharePoint, and Teams data between tenants, that too without any data loss.
Q.3. How much data can 250 Microsoft 365 users contain?
Ans: Uncertain. There doesn’t exist any particular number or fixed volume of data for 250 users. Rather, the total data size largely depends on the individual mailbox, OneDrive, SharePoint, and other workloads.
Q.4. Can Aryson migrate multiple Microsoft 365 users in bulk?
Ans: Yes. When it comes to the software, it can migrate multiple users at the same time via its CSV import feature. With the help of this functionality, large firms can load multiple users simultaneously and support bulk migration. Thus, there is no need to configure each account individually.
Q.5. Does the Aryson tool support admin-level authentication for tenant migration?
Ans: Yes. The software allows users to log in to their tenant account via Admin Mode and authenticate the source and destination accounts. They just have to select data from multiple sub-users to migrate data.
Q.6. Can I migrate only selected data from a Microsoft 365 user?
Ans: Yes. With the help of the Aryson Tenant to Tenant Migration Tool, you can easily migrate selected data using the date range and other folder filters provided by the software.
Q.7. Why should a 250-user migration be performed in batches?
Ans: It is considered a better practice to perform a migration on 250 users or more in batches, rather than performing a cutover migration. For this, first migrate a test pilot batch and monitor the progress closely. If there are zero errors, perform migration on the remaining dataset. However, if you use professional software, you may eliminate all this, migrate 250 users in bulk, and save time.
Q.8. Can I monitor the migration progress for 250 users?
Ans: Yes. The monitoring panel of the Aryson Tenant-to-Tenant Migration Tool allows you to track the migration process. You may check the total number of migrated folders, the failed ones, and the ongoing migration at every step.
Q.9 What is cross-tenant user data migration in Microsoft 365?
Ans: It is the process of moving the workload data from one tenant account to another in a Microsoft 365 environment. These workloads might include Exchange Online mailboxes, SharePoint sites and document libraries, OneDrive data and Teams conversations.
Q.10 Which is the best tool to migrate 250+ Microsoft 365 users from one tenant to another?
Ans: The Aryson Tenant-to-Tenant Migration Tool is the best tool to migrate 250+ Microsoft 365 users from one tenant to another. This is because this software comes with both CSV file importing and admin login. On top of that, it also provides users with a free demo version that can be used to evaluate the software’s performance.
About The Author:
Harshita Sachdeva, a professional technical writer at Aryson Technologies, specialize in delivering clear, hands-on documentation for data management, migration, and recovery solutions. With a meticulous, reader-first approach, I break down complex technical processes into simple, actionable content - helping IT professionals and decision-makers tackle challenges efficiently.
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