Shared Mailbox OWA Inconsistent Behavior

Question

There are two ways of opening Shared Mailbox in OWA,

1. Clicking on your user profile, and select "Open another mailbox"
2. Right-clicking on your Folders, and select "Add shared mailbox"

Based on the documentation, https://learn.microsoft.com/en-us/office/dev/add-ins/outlook/delegate-access, you need to have SupportsSharedFolder permission explicitly set to true in your add-in manifest in order to make your add-in available on shared mailbox item.

For option 1, I am able to open any add-in that doesn't have SupportsSharedFolder permission.

For option 2, all add-in that doesn't have SupportsSharedFolder is not shown in the list of available add-ins. (Expected behavior)

Notes: Outlook desktop client is consistent with option 2, it is not showing any add-in that doesn't have SupportsSharedFolder permission.

Is option 1 an expected behavior from OWA? If its a bug, do we have a timeline for a fix?

Similar question posted a while back, Make Outlook add-ins working with Office 365 shared mailboxes however there is no definitive answer from MSFT team.

Answer 1

We were able to repro the issue. This is a new feature ask as Add-ins are not supported on other open mailboxes. We track Outlook add-in feature requests on our user-voice page. Please add your request there. Feature requests on user-voice are considered when we go through our planning process.