Resolve Outlook Shared Mail Sync

On new Windows 11 laptops running classic Outlook in Cached Mode, any shared mailbox that is auto-mapped through user permissions stops refreshing: new messages arrive on the server yet show up late – or not at all – in users’ view. The same mailboxes work perfectly on older Windows 10 machines.

We run a hybrid setup: some mailboxes live in Microsoft 365 Exchange Online, others on-premises. Because the affected shared mailboxes are granted automatically, end users never add them manually; Outlook simply picks them up through Autodiscover. The glitch appears only on Windows 11 devices and only in these auto-mapped stores.

I need an Exchange & Outlook specialist to:

• Analyse the hybrid topology (Exchange Online, on-prem server, Azure AD Connect, Autodiscover flow, Outlook profile settings, Cached Mode sliders, OST generation, registry keys, Conditional Access, etc.).
• Pinpoint why the cache fails to update and deliver a clean, repeatable fix that I can roll out to every Windows 11 workstation.
• Document the root cause, registry or policy changes, PowerShell commands, or transport adjustments you apply, so I can reproduce them.

Acceptance criteria: shared mailboxes refresh in real time (within normal sync tolerance) on at least two pilot Windows 11 laptops running classic Outlook after your remedy is applied, with no adverse effect on primary mailboxes or Windows 10 devices.

I can provide remote access to a test machine, Outlook logs, and hybrid connector details. Let me know what additional diagnostics you require and an estimated timeline for getting us back to normal sync performance.