Access on-prem Exchange mailbox with AAD Joined device
We have setup Exchange 2016 Hybrid latest CU etc.
Moved my mailbox to O365 and all works well, free busy, autodiscover etc.
Now i have a test Windows 10 device joined to Azure AD (not hybrid).
Accessing my mailbox via Outlook is SSO but i also have a shared mailbox to open that is on-premises and this one causes a authentication prompt.
Is the authentication prompt for the on-premises mailbox expected behaviour or can we achieve SSO ?