Microsoft To Do – Cannot join shared lists between two personal Microsoft accounts

Hello Microsoft Support Community,

I am experiencing a persistent issue with Microsoft To Do list sharing between two personal Microsoft accounts.

Account configuration:

• Account 1: Personal Microsoft account registered with Gmail.
• Account 2: Personal Microsoft account using Hotmail.
• Subscription: Microsoft 365 Family.

Both accounts can independently sign in to Microsoft To Do and use the application without any issues.

Problem:

Neither account can join a list shared by the other.

The following error appears:

"Lists can only be shared between personal accounts, or between work or school accounts in the same organization."

Both accounts are personal Microsoft accounts, so this restriction should not apply.

Troubleshooting already completed:

1. Verified that both accounts are personal Microsoft accounts.
2. Tested sharing in both directions (Gmail → Hotmail and Hotmail → Gmail).
3. Created completely new test lists.
4. Generated new sharing invitation links.
5. Tested using Chrome Incognito mode.
6. Tested across Chrome browser and Android devices.
7. Confirmed that both accounts can access Microsoft To Do independently.

The problem persists in every scenario.

Assistance requested:

Could you please investigate the following?

1. Whether either account is incorrectly identified as a work or school account by the To Do sharing service.
2. Whether there are account-level restrictions affecting list sharing.
3. Whether there is a backend issue with the Microsoft To Do sharing service.
4. Whether this issue can be escalated to the Microsoft To Do product or engineering team.

I would appreciate technical assistance rather than further generic recommendations to reinstall the application or clear browser cache, as these steps have already been effectively ruled out.

Thank you for your assistance.