How to manage switching to a new tenant

Question

How to manage switching to a new tenant

Nick Ralph 15

My employer has switched to a new IT provider and new Microsoft Tenant but I cannot seem to remove the old tenant from automatically being picked up when trying to put in the same email address. How do I remove the connection to the old tenant? I am on a personal MacBook Pro (fully updated). I also need access to 3 other tenants for other organisations I am involved in working with but the problem is with my primary one. Every time I try to add an account to Outlook, it picks up the old tenant's details.

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3 answers

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Answer 1

Nick Ralph 15

Thank you for the advice which is greatly appreciated. The thing that worked was finding the migration name which was then able to pick up the correct tenant and then picked up automatically the correct email address. Hugely relieved to have this sorted. It is slightly complicated. Appreciate the detailed advice had this not worked. What a helpful community!

Ruby Nguyen 2,800 Reputation points Independent Advisor

2026-09-24T16:54:14.2733333+00:00

Hi Nick,

It's wonderful news that your issue has been resolved. Thank you for providing updates on the status of your case.

If you have any concerns or questions in the future, please don’t hesitate to reach out. Not only will I be happy to assist you, but all users in the Q&A forum will also do their best to provide support and guidance.

Thank you once again for your precious time and engagement.
Graham Campbell 0 Reputation points

2026-09-29T03:24:53.1366667+00:00

@Nick Ralph Can you please explain the "migration name" for a migration newb here? And how you used this info in outlook to resolve the issue?
Nick Ralph 15 Reputation points

2026-09-30T15:54:54.9633333+00:00

Graham, I am in no way expert in these matters but I will try. The email address you want to use is one thing, but there seems to be an interim step during which things are transferred which inserts the word on migration after the @, as in ******@onmigration.yourdomain.com and is the means by which it is recognised. I cannot really tell you more than that because I don't really understand any more than that!
Graham Campbell 0 Reputation points

2026-09-30T22:50:50.1133333+00:00

@Nick Ralph I have never seen the onmigration sub domain used before. I've only ever seen the onmicrosoft name used used like this [email protected] . Are you sure it's onmigration and not onmicrosoft?
Nick Ralph 15 Reputation points

2026-10-01T15:24:16.7666667+00:00

You are quite right. Apologies. I was trying to do it all from memory and this is not familiar territory for me.
Graham Campbell 0 Reputation points

2026-10-01T22:09:42.2166667+00:00

@Nick Ralph Thanks for clearing that up. I'll let you know if that works for my customer too.

Answer 2

Good day Nick,

This issue usually occurs when Outlook or macOS still has saved credentials from the previous Microsoft 365 tenant. As a result, Outlook continues to use the old sign in information instead of prompting for a fresh connection.

Before troubleshooting, please confirm with your current IT provider that the account has been created in the new tenant, assigned a Microsoft 365 license and that the domain migration has been completed.

Here are some options you can follow:

Option 1: Remove the old account from Outlook

Open Outlook.

Select Tools > Accounts > Select the account connected to the previous tenant.

Select Manage > Remove Account > Select Continue.

Quit Outlook completely.

Reopen Outlook.

Go to Outlook > Settings > Accounts > Add Account.

Enter your email address and sign in with your current organization's credentials.

Option 2: Clear saved credentials from Keychain Access

Please note that this can sign you out of other Microsoft 365 accounts on the Mac, so make sure you have access to those account credentials and authentication methods before proceeding.

Close Outlook and all Microsoft 365 apps.

Open Finder > Applications > Utilities > Keychain Access.

Search for the affected email address and remove entries related to the previous organization's tenant.

Search and delete all references to the following items:

Exchange

Office

Microsoft Office Identities Cache

Microsoft Office Identities Settings

ADAL

Restart the Mac.

Open Outlook and add the account again.

Option 3: Create a new Outlook profile

Close Outlook.

Open Applications > Microsoft Outlook.

Right click Outlook and select Show Package Contents.

Open Contents > SharedSupport.

Launch Outlook Profile Manager.

Create a new profile and set it as the default profile.

Restart Outlook.

Add the account using the new organization's credentials.

Option 4: Remove old Office license information

Use this step only if Office apps still show the previous organization's tenant for activation.

Close all Microsoft 365 applications.

Download and run the Microsoft Office License Removal Tool.

Complete the prompts and restart the Mac.

Open any Office application.

Sign in with the account licensed by your current organization.

This article provides further guidance on the topic: How to remove Office license files on a Mac | Microsoft Support

Option 5: Check device registration

If the Mac was previously enrolled through Intune Company Portal app or configured for organizational sign in:

Note: If your Mac isn't enrolled, you can skip this option. If you're unsure, please contact your new IT provider to verify whether the device is enrolled. In case you do not know who is your IT admin, kindly refer to this article: How do I find my Microsoft 365 admin? - Microsoft Support

Open Company Portal app in your Mac > Open Preferences.

Check whether the device is still connected to the previous organization's tenant.

If it is, select Deregister and restart the Mac.

Register the device with the current organization only if instructed by your IT provider.

If the previous organization's tenant still manages the device and deregistration is unavailable, please contact the IT provider and ask them to remove the device from management.

I hope these steps help you remove the previous tenant connection and successfully connect Outlook to the correct organization. If you have any questions or need further support, please don’t hesitate to reach out at any time.

Thank you for your patience and understanding.

If you have any extra questions about this answer, please click "Comment".

Answer 3

On a Mac with the same email address now tied to a new Microsoft 365 tenant, the old tenant is usually being selected because cached sign-in state is still present or because the address is colliding with another Microsoft account or tenant record.

Try this in order:

Close all browser windows completely before testing again.
If multiple browser tabs or windows are open, some can keep the old identity active even after sign-out.
When working with multiple tenants, use separate browser sessions.
Use a different browser or an in-private/incognito window for each tenant. This is the recommended way to stay signed in to multiple Viva Engage tenants at once, and the same approach helps avoid tenant mix-ups during Microsoft sign-in flows.
In Outlook for Mac, remove the affected account and add it again.
Go to Tools > Accounts... and remove the old account entry if it is still present. Then add the account again with Tools > Accounts... > + Add Account.
During add-account, manually choose the provider if Outlook selects the wrong one.
When adding the account, if the provider is not selected correctly, use Not [Google, iCloud, Yahoo, etc.]? and manually choose the correct provider before continuing.
If the sign-in prompt shows “Which account do you want to use?”, resolve the account collision.
That prompt means there are two Microsoft accounts using the same email address: a Work or school account and a Personal account. To stop that prompt, one supported option is to rename the personal Microsoft account by changing its primary alias in Manage how you sign in.
If Outlook still keeps routing to the old tenant, try signing in with the new tenant’s onmicrosoft.com account name instead of the unchanged email address.
A documented Microsoft Q&A workaround for this exact migration pattern on Outlook for Mac is to sign in using the mailbox username at the new tenant’s onmicrosoft.com domain so Outlook binds to the new tenant instead of the old one.
If the problem continues, the old tenant association likely must be removed by an administrator.
Accepted Microsoft Q&A guidance for this scenario is that the address may still exist in the former organization’s tenant, or as a guest user there. In that case, the former organization’s Global Administrator needs to remove the account’s association with that tenant.
If the issue is with the primary employer tenant after a tenant migration, ask the current IT admin to investigate tenant-side configuration.
Microsoft support guidance for tenant redirection problems states that if sign-in goes to a different tenant than intended, this is a configuration issue that only the tenant admin can solve.

For the 3 other organizations, keep each tenant isolated by browser profile, separate browser, or incognito/private window. That is the cleanest supported way to avoid one tenant being automatically reused for another.