How do I keep a copy of emails on the server with Outlook?
Open Outlook interface, and click on "Tools -> E-mail Accounts".
Select "View or change existing e-mail accounts" and click "Next".
Choose the account that you would like to edit and click "Change".
Then click "More Settings", and navigate to the "Advanced" tab.
Place a check mark next to the option for "Leave a copy of messages on the server"
Click "OK", then "Next", then "Finish".
You have now set Microsoft Outlook to leave a copy of all downloaded emails on the server so they are still accessible via webmail.