Same issue here, 1.5 iso install, user and mail setup with webmail, setup a pop 3 retrieval, all mail services are running, external retrieval is stopped and the start button has no obvious effect.
Like to get this working because this is the whole reason for the ebox install, to retrieve mail from an online host and share via imap.
One point of concern, there seems to be no options in the gui for external retrieval for leaving the messages on the server for any period of time or controlling deletion from the server, or even what the default is.
Does anyone know how this works?