How to ensure a secure and seamless migration of company email, OneDrive, and Teams data when transitioning the corporate email domain from .sg to .my, while also providing the IT department with a clear operational guide.

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How to ensure a secure and seamless migration of company email, OneDrive, and Teams data when transitioning the corporate email domain from .sg to .my, while also providing the IT department with a clear operational guide.

Kelvin Ng Yu Hang 25

Subject : Migration Plan – Transition from `.sg` to `.my` Domain

Core Requirements

Hi Microsoft Teams , The company has decided to stop using the .sg domain email addresses and transition to .my domain email addresses.

Key concern: During the migration, OneDrive and Teams files must remain accessible without disruption.

Confirmation needed: As long as the Microsoft 365 primary account (Global Administrator) performs the domain and account migration in the backend, all data continuity will be preserved. Users should not be required to manually download and re-upload files, thereby avoiding risks of broken links or lost connections.

Objective: Provide a formal migration checklist and documentation for IT and management teams, ensuring clarity that this is the fastest and safest approach.

Need for your support.

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Hani-Ng 11,155 Microsoft External Staff Moderator

Hi Kelvin Ng Yu Hang

First, I hope you understand that this forum is a peer-to-peer community. While members can share advice and experiences only. So, based on my research and understanding that your proposed approach performing the domain and account update within the same Microsoft 365 tenant under a Global Administrator account is correct and perfectly aligns with Microsoft best practices. This method ensures a seamless transition while preserving all existing data and service continuity.

As long as the migration is performed within the same tenant:

All OneDrive, SharePoint, and Microsoft Teams data will remain fully intact.
Existing file links, sharing permissions, and collaborations will continue to function without disruption (Microsoft automatically redirects old links to the new URLs).
No manual download or re-upload of files is required.
User mailboxes, calendars, and Teams history will remain unchanged.

This is because Microsoft 365 services are tied to the user's backend account object (Entra ID), not the email domain itself. Updating the domain only changes the user identity (UPN/email address), not the underlying data.

Here is a recommended migration checklist you can review:

Pre-Migration Preparation

Add and verify the .my domain in the Microsoft 365 Admin Center.
Ensure DNS ownership is validated.
Review any third-party applications or systems using the existing .sg email addresses for SSO (Single Sign-On).
Communicate upcoming changes to all users, noting they will need to sign back into their apps.

Domain Configuration & DNS Cutover

Configure all required DNS records for the .my domain (MX, Autodiscover, SPF, DKIM, etc.) so Microsoft 365 is ready to receive mail for the new domain.
Set .my as the default domain for the tenant.

User Account Updates

Update the User Principal Name (UPN) for each user to .my.
Change the primary SMTP address to .my.
Crucial: Retain the .sg addresses as secondary aliases on the accounts to prevent any inbound mail disruption.

Validation

Verify user access to Outlook, OneDrive, and Teams via the web browser.
Confirm that files, permissions, and links remain accessible.
Test mail flow (inbound and outbound) for both domains.

Post-Migration & User Actions

Continue to support .sg as a secondary alias domain indefinitely, or until you are certain it is no longer in use.
Update external systems, email signatures, and dependencies.

For the IT Helpdesk, please note:

-App Re-authentication: Users will be prompted to sign in again across applications such as Outlook, Teams, and Office desktop apps after their username is updated.

-OneDrive Desktop Sync: Because the UPN change alters the personal SharePoint URL in the backend, the local OneDrive Sync Client on users' PCs may stop syncing. IT should instruct users to go to OneDrive Settings > "Unlink this PC" and sign back in with their new .my address to seamlessly re-establish the connection. No data is lost during this process.

-OneNote: Desktop OneNote notebooks may need to be closed and re-opened to sync properly with the new URL.

I hope this information helps and if you have any question, please feel free to ask!

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Hani-Ng 11,155 Reputation points Microsoft External Staff Moderator

2026-05-15T05:46:32.5966667+00:00

Hi Kelvin Ng Yu Hang

I just wanted to follow up to see if you need any additional information regarding this matter. Please don’t hesitate to reach out!
Kelvin Ng Yu Hang 25 Reputation points

2026-05-18T05:46:33.84+00:00

Hi @Hani-Ng **,**Thank you for the detailed explanation and migration checklist. I appreciate the clarification that performing the domain and account update within the same Microsoft 365 tenant under a Global Administrator account aligns with Microsoft best practices.

I will proceed with the recommended steps, including:

Adding and verifying the new .my domain in the Admin Center

Configuring DNS records and setting .my as the default domain

Updating user UPNs and primary SMTP addresses while retaining .sg as secondary aliases

Validating access to Outlook, OneDrive, Teams, and mail flow for both domains

I will also ensure users are informed about re-authentication requirements and provide IT Helpdesk guidance for OneDrive and OneNote adjustments.

Thank you again for the comprehensive checklist. This gives me confidence to move forward with the migration.

Best regards, Kelvin Ng Yu Hang
Kelvin Ng Yu Hang 25 Reputation points

2026-05-18T06:43:09.68+00:00

Hi @Hani-Ng but now on company is no only change domain is “Tenant-to-Tenant Migration" so the way will be different right?
Kelvin Ng Yu Hang 25 Reputation points

2026-05-18T06:48:33.28+00:00

Company previous is purchase Microsoft 365 Singapore , now next month stop continue SG account ，and already purchase Microsoft 365 Malaysia, how i should i can do safe moving all data document to new account?
Hani-Ng 11,155 Reputation points Microsoft External Staff Moderator

2026-05-18T08:39:02.42+00:00
Hi Kelvin Ng Yu Hang

You are correct, this is a different scenario. In your original case (same tenant), no data migration was required. However, since your company is stopping the Singapore tenant and moving to a newly purchased Malaysia tenant, this becomes a tenant-to-tenant migration, which means Microsoft treats them as completely separate environments.

In this situation, there is no native “handover” of data in the backend. All workloads such as Exchange Online, OneDrive, SharePoint, and Teams must be migrated from the SG tenant to the MY tenant. From a technical standpoint, data in Microsoft 365 is bound to the tenant itself, not just the domain. Because of that, changing tenants means you are effectively moving data between two different organizations.

If your concern about OneDrive and Teams continuity is valid, but in a tenant-to-tenant migration:

Data will not automatically remain accessible

OneDrive and SharePoint URLs will change

Teams associations and chat history may not fully carry over depending on the method used

Microsoft documentation also explains that even a simple UPN/domain change already updates OneDrive URLs and requires propagation, although the data remains intact within the same tenant. In a cross-tenant scenario, this effect is more significant because the data is being moved, not just updated.

The safest approach is to treat this as a structured migration project rather than a simple admin change. You should keep the SG tenant active during the entire process. Do not cancel it until all data is confirmed moved and validated in the MY tenant.

For small environments, manual methods (download/upload, PST export/import) are possible, but they are not recommended because they introduce risks such as permission issues, missing metadata, and potential impact on users. For most organizations, the standard practice is to use a migration solution.

For high-level safe migration flow, a typical approach would be:

First, prepare the MY tenant with users and licenses.

Then migrate OneDrive and SharePoint data.

After that, migrate mailboxes.

Recreate or migrate Teams structure and files.

Finally, switch DNS (MX records) to the MY tenant and move users over.

Only after everything is validated should the SG tenant be decommissioned.

I hope this information helps.
Kelvin Ng Yu Hang 25 Reputation points

2026-05-19T01:06:11.97+00:00
Yup company was done provide new licenses by tenant “.com.my” in Malaysia Microsoft 365 for me.
After that how is the safe step for

Migrate OneDrive and SharePoint data.

Migrate mailboxes.

Migrate Teams structure and files.
Hani-Ng 11,155 Reputation points Microsoft External Staff Moderator

2026-05-19T09:01:17.96+00:00

Hi Kelvin Ng Yu Hang

Since a different set of requirements from the original question, I recommend creating a new thread and including these details there. This helps avoid mixing multiple issues in one discussion and allows moderators to focus on your specific use case more effectively.

Creating a separate thread will also enable us to request additional information via private message if needed, while helping protect personal or organizational data.

Thank you for your understanding.
Kelvin Ng Yu Hang 25 Reputation points

2026-05-20T01:24:35.8633333+00:00

Sure Thanks to your assist，hope that you can continuo to the new thread.

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How to ensure a secure and seamless migration of company email, OneDrive, and Teams data when transitioning the corporate email domain from .sg to .my, while also providing the IT department with a clear operational guide.

Subject : Migration Plan – Transition from .sg to .my Domain

Core Requirements

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Your answer

Subject : Migration Plan – Transition from `.sg` to `.my` Domain