Hey everyone, I ran into a strange issue where our users are being prompted to sign in to a different Office 365 tenant when they try to access shared mailboxes. The Service Desk got a report from one of our users who experienced this, and when they tested it with their own account, they faced the same login screen for another tenant. This didn't seem tied to any specific documents or emails since it popped up unexpectedly after they added the mailboxes. From the screenshots I received, it looks like the system is trying to access some default Microsoft Office app related to other tenants that, while industry-related, are not the ones we typically use. The error states that the user's account from our identity provider doesn't exist in that other tenant, but I'm not sure why it would try to connect to it at all. I've searched for similar issues but found nothing, so I'm hoping someone here might have experienced this before and can help out!
1 Answer
I had this happen to me too, and the sysadmins here thought it was a phishing attempt at first. It’s definitely odd that it relates to shared mailboxes. I’d recommend opening a ticket with Microsoft and requesting that it gets escalated to their Entra ID engineering team for some clarity. I’m still waiting on an answer from Microsoft myself!
Thanks for the insight! I've already opened a ticket, but I’m a bit skeptical since the last time it took them ages to respond and nothing changed. Fingers crossed this one gets sorted out quicker!