If you would like to leave a copy of email at the server when configuring microsoft outlook, you may do so using the following steps below:

Go to the top navigation bar "Tools >>  E-mail Accounts.. >> Add / View or Change E-mail accounts"

Select the email accounts that you would like to modify, then select "More Settings >> Advanced"

You can configure the setting at the Delivery section.

Below is a print screen of the final screen that you will need to reach for the configuration: