How can I turn off calendar notifications for a specific account

Disconnect the obsolete company account from Windows first, because a Windows-level account connection can continue generating desktop sign-in notifications even when Outlook.com is closed.

1. Disconnect the old work account from Windows

1. Open Start → Settings → Accounts → Access work or school.
2. Expand the old company account.
3. Select Disconnect, then Yes.
4. Restart Windows.
5. Wait several minutes and confirm that the sign-in notification no longer appears.

Disconnecting removes that account’s sign-in information and organizational connection from this PC; it does not delete the online account. ^1^

2. Remove any separate calendar account registration

If the notification returns, the account may also be registered separately for email, calendar, and contacts:

1. Open Settings → Accounts → Email & accounts.
2. Under Accounts used by email, calendar, and contacts, select the obsolete company account.
3. Select Manage, then choose the available option to remove the account from this device.
4. Also check Accounts used by other apps and remove the old account there if it appears.
5. Restart Windows again.

If the legacy Mail or Calendar app is still installed, open it and select Settings (gear) → Manage accounts → old company account → Delete account from this device. Microsoft’s legacy-app procedure is available under Delete an email account from Mail and Calendar apps, linked from the classic Outlook removal guidance. ^2^

Because you no longer need the old data, removing the account is appropriate. Any locally cached mail or calendar data for that account can be deleted.

3. If the account is also configured in Outlook for Windows

This is unnecessary for Outlook.com in a browser, but apply the matching desktop-app procedure if Outlook is installed.

New Outlook:

1. Open View → View settings or File → Account info.
2. Select Accounts → Your accounts.
3. Beside the old account, select Manage → Remove.
4. Choose removal from this device when prompted.

Removing an account deletes its offline cached content. Be cautious with Remove from all devices, because Microsoft warns that cloud-only calendar items for some non-Microsoft accounts could be permanently lost. ^3^

Classic Outlook:

1. Open File → Account Settings → Account Settings.
2. Select the obsolete account.
3. Select Remove → Yes.

This removes the account and locally cached content from Outlook without deactivating the provider’s online account. ^2^

4. Clear saved credentials only if prompts continue

If the account is absent from all locations above but Windows still requests its password:

1. Search for and open Credential Manager.
2. Select Windows Credentials.
3. Remove credentials that clearly reference the obsolete company account or organization.
4. Restart Windows.

Do not remove credentials belonging to your active personal or work accounts. Credential cleanup is a fallback for an old organizational identity that remains cached after disconnection. ^4^

References

1. Manage User Accounts in Windows | Microsoft Support
2. Remove or delete an email account from classic Outlook for Windows | Microsoft Support
3. [New Outlook](https://support.microsoft.com/outlook/getstarted/add-an-email-account-to-outlook-for-windows#remove-an-account-in-new-outlook)
4. how to remove an old work account - Microsoft Q&A