Block OneDrive for all users on tenant

[Kevin Egan]

We have recently migrated all our users to a new M365 tenant but have found that users with OneDrive on their personal devices are still able to sign in and save files to their old OneDrives. What would be the best way to stop them doing this? a conditional access policy?

[#2]

Some of the third-party migration tools offer "reconfiguration" of the OneDrive client, I take it that was not part of your process? There are few options to consider. CA policy should do, and if those are managed devices you can use the GPO/reg keys to limit which tenants OneDrive can access: https://learn.microsoft.com/en-us/sharepoint/use-group-policy#allow-syncing-onedrive-accounts-for-on...
Depending on whether any use remains for apps within the old tenant, you can also consider disabling all accounts therein, or just resetting their passwords. Revoking all tokens can speed up the process of blocking access.

[#3]

@Kevin Egan 

Welcome to the Microsoft community, my name is Recep I'll be happy to help you today.

To block OneDrive for all users on your tenant, here are some of the options you can utilize:

1. Conditional Access Policy: You can create a conditional access policy to block access to OneDrive for all users on your tenant. This policy will apply to all devices and platforms that users use to access OneDrive. You can configure this policy to block access to OneDrive based on various conditions such as device type, location, and more.

2. Manage User Permissions: You can modify the user profile properties of each user and disable their OneDrive access. However, this method is not scalable if you have a large number of users.

3. Restrict OneDrive Access by Security Group: You can restrict OneDrive access to only users in specified security groups. This method is useful if you want to allow some users to access OneDrive while blocking others.

4. Block OneDrive Use from Within Microsoft 365 Apps for Enterprise: You can use Group Policy settings and registry modification to block access to OneDrive from within the Office applications.

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