Syncing a SharePoint site's files with the OneDrive desktop client: using a personal Microsoft Account

Question

Example scenario:

• Let's say we have a regular 365 tenant called "TenantCompany", that have a SharePoint Online site such as: https://tenantcompany.sharepoint.com/sites/OurCompanySite/
• "User A" with 365 tenant login [email protected], shares the "OurCompanySite" out to an external user, "User B": [email protected]
• [email protected] is simply a regular personal "Microsoft Account". "User B" does not have a 365 account at all.
• [email protected] can browse the files in their web browser at: https://tenantcompany.sharepoint.com/sites/OurCompanySite/Shared%20Documents/ - this works fine
• But when [email protected] tries to click "Sync", to have the files sync down to their desktop computer using OneDrive, I get error when trying to login with the OneDrive desktop client:
  • "You can't sign in here with a personal account. Use your work or school account instead."

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Question 1: Is it even meant to be technically possible for [email protected] to sync the files from the "OurCompanySite" SharePoint site? Purely with their personal Microsoft account?

I'm sure I've seen this work in the past, but it was very inconsistent from all my experiments. It seemed to work like 15% of the time. And sometimes after it was working for a while it would stop.

To start with I'm simply trying to figure out whether this is even meant to be possible or not, i.e. a simply "yes" or "no" answer to this question. Because without this, trying to answer #2 has been very hard...

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Question 2: If it can be done, what it the best procedure to get it working?

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Question 3: If the answer is "No", why does Microsoft display the "Sync" button to begin with? Other buttons that they can't use are normally hidden.

Answer 1

This scenario is not possible. The Guest user must be using an M365 Work or School account.

The documentation is available here.