/
Outlook - PST Reached Maximum Size

Outlook - PST Reached Maximum Size

Problem

Users may encounter warnings or errors indicating their Outlook PST file has reached its maximum size. This guide outlines steps to resolve the issue by enabling Cached Exchange Mode.

Solution

Turn Cached Exchange Mode on

  1. Select File > Account Settings > Account Settings.

  2. Select the Exchange or Microsoft 365, and then select Change.

  3. Under Offline Settings, check Use Cached Exchange Mode.

    (If you're a Microsoft 365 subscriber with semi-annual updates, under Offline Settings, check Use Cached Exchange Mode to download email to an Outlook data file.

  4. Exit, and then restart Outlook.

If you want to turn off Cached Exchange Mode, repeat the steps, but clear Use Cached Exchange Mode.

Older mail not cached locally remains available via Outlook on the Web (OWA) or by adjusting the sync slider if needed.

Once the user is successfully using Cached Exchange Mode, you may close the old PST by right-clicking it in the folder pane and selecting Close [PST Name].

If the Cached Exchange Mode option is greyed out, verify the account type (must be Microsoft Exchange or Microsoft 365) and check if Outlook is in Online Mode via Group Policy.