Disablesyncsliderforsharedmailbox Jun 2026

★★★★★ (Essential for hybrid environments)

This is a massive quality-of-life improvement for Exchange administration.

Increases local OST file size and initial sync time. disablesyncsliderforsharedmailbox

The registry value is a specialized configuration used in Microsoft Outlook (2016 and later) to control how much email is stored locally for shared mailboxes. By default, Outlook limits the synchronization of shared mailboxes to a specific timeframe—typically the last 12 months—to manage local storage and improve performance. Purpose and Functionality

| Problem | Solution | |---------|----------| | Setting doesn’t work | Ensure Outlook is closed when editing registry. Confirm path matches your Office version. | | Outlook still only shows 12 months | Right-click the folder > > Clear Offline Items > restart Outlook to force a full resync. | | Mac version not respecting command | Use Outlook’s account settings to set "Download all messages" instead. | | OST file too large | Revert setting to 0 , then run Mailbox Cleanup tools. | By default, Outlook limits the synchronization of shared

For developers or those comfortable with API calls, Microsoft Graph provides access to mailbox settings.

[PSCustomObject]@ MailboxName = $Mailbox DisableSyncSlider = $DisableSyncSlider | | Outlook still only shows 12 months

Or specifically querying mailbox settings: