Fix Outlook Shared Mailbox Not Updating

Shared mailbox sync problems usually come from cached mode behavior, stale Outlook profiles, permissions propagation, or large mailbox folder counts.

Quick answer: Test Outlook on the web first, confirm permissions, disable Download Shared Folders for heavy shared mailboxes, rebuild the Outlook profile if needed, and check whether the issue affects one user or everyone.

Fast isolation

If Outlook on the web is current but desktop is stale, the problem is local client/cache.
If both are stale, check mailbox, permissions, transport, rules, or service health.
If only one folder is stale, check folder size and cached shared folder behavior.

Desktop Outlook cached mode fix

For large shared mailboxes, disable shared folder download. This keeps the primary mailbox cached while reducing shared mailbox OST pain.

Outlook > Account Settings > Account Settings
Select account > Change > More Settings
Advanced tab
Uncheck: Download shared folders
Restart Outlook

PowerShell permission checks

Get-MailboxPermission shared@company.com | Where-Object {$_.User -notlike 'NT AUTHORITY*'}
Get-RecipientPermission shared@company.com

When to rebuild the profile

Rebuild the Outlook profile after you confirm OWA is healthy and only one desktop client is stale. Do not rebuild profiles for everyone until you know the scope.

Large mailbox warning

A shared mailbox with huge folders, many delegates, and cached shared folders enabled will eventually become painful. For operations mailboxes, use archive policy, folder hygiene, and clear ownership rules.

Best first test: Compare OWA and desktop before changing permissions. That prevents wasting time on the wrong layer.

About the author

Jason Purvis works in enterprise monitoring and IT operations, with hands-on experience across ServiceNow ITOM/Event Management, SolarWinds-style infrastructure monitoring, Microsoft 365 operations, alert routing, and incident process improvement.