Retrieving older emails - Method : Changing Cache Exchange Mode

Cache Exchange mode is a setting in Outlook that determines the period for which email messages are preserved in local storage used by Outlook installed on a computer for accounts using Microsoft Exchange email services.

1. Click File > Account Settings > Account Settings to configure options for a user. If Outlook is configured to use multiple accounts, select the email account needed in the drop-down menu on this page.
2. On the Account Settings page, click the account needed, then click Change.

3. Check Cached Exchange Mode settings, which are available for Exchange accounts only. By default, the Outlook client in Windows uses local storage on a computer to store emails for 1 year. Then older emails are deleted from the local Outlook client storage.

   Move the slider to the right from 1 year to All. Click Next and finish the configuration, then reboot Outlook for the changes to take effect. After that, your old emails should not be deleted after three or twelve months.

This setting can also be tuned in Windows Registry and in the group policy editor.