A user is logged in to Zivver in Outlook Web App (OWA) with their personal mailbox. When the user switches to a delegated shared mailbox, a Zivver login screen appears again instead of the existing session being carried over.

Cause

Microsoft is migrating OWA from outlook.office.com to a new domain, outlook.cloud.microsoft. This migration does not always reach every mailbox at the same time. The personal mailbox can already be on the new domain while the shared mailbox is still on the old domain, or the other way around.

The automatic login for shared mailboxes only works when both mailboxes use the same OWA domain. The Zivver add-in stores the active session in the local storage of the browser, and the browser keeps this storage separately for each domain. A session on one OWA domain is therefore not available on the other domain. Zivver cannot change this. The session carries over again as soon as Microsoft has migrated the whole tenant.

Solution

1. Open the personal mailbox in OWA.
2. Check the address bar of the browser.
   The address starts with either outlook.office.com or outlook.cloud.microsoft.
3. Open the shared mailbox in OWA.
4. Check the address bar of the browser.
5. Compare the two addresses.
   Are both addresses the same? Then the domain is not the cause. Follow the steps in Troubleshooting “Login to delegate account failed” error.
6. Ask your Microsoft 365 administrator whether the OWA migration can also be completed for the shared mailbox.
7. Make sure that cookies and pop-ups are allowed for both OWA domains.
8. Close the browser tab and open OWA again.
9. Switch to the shared mailbox.
   The Zivver login screen no longer appears.

Tip

While the domains are different, open the shared mailbox in a separate browser window. Opening the mailbox this way is a reliable workaround.

Does the login screen still appear after these steps? A partial rollout by Microsoft is then the most likely cause. Confirm this with your Microsoft 365 administrator.