POP3 & IMAP are different access methods for reading the same mailbox on a mail server.
In WLM set the POP3 a/c to always Leave a Copy on the Server. Then the same a/c can be used as IMAP from the Win8 mail program.
1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU => 2010: Orange 16 Meg LLU => 2011: Orange 19 Meg WBC