Server Email Settings

When I first began getting emails on multiple devices, I had to click a setting to retain the emails on the server so that would download to all devices, not just the one that got there first.  I recently began using outlook.com to sync mail across all of my devices and I am pleased and comfortable enough with it now to flip that setting to delete rather than retain emails.  But I can't locate where this setting, or preference, is accessed.  Can anyone help me?